Forming catalytic sites from reducible silver-heterocyclic complexes

ABSTRACT

A non-aqueous metal catalytic composition includes (a) a complex of silver and a hindered aromatic N-heterocycle comprising reducible silver ions in an amount of at least 2 weight %, (b) a silver ion photoreducing composition in an amount of at least 1 weight %, and (c) a photocurable component, a non-curable polymer, or a combination of a photocurable component and a non-curable polymer. This non-aqueous metal catalytic composition can be used to form silver metal particles in situ during suitable reducing conditions. The silver metal can be provided in a suitable layer or pattern on a substrate, which can then be subsequently subjected to electroless plating to form electrically-conductive layers or patterns for use in various articles or as touch screen displays in electronic devices.

RELATED APPLICATIONS

Reference is made to the following copending and commonly assignedpatent applications, the disclosures of which are incorporated herein byreference:

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla andDonovan) entitled “Forming Catalytic Sites from Reducible SilverComplexes” (Attorney Docket K001768/JLT);

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla andDonovan) entitled “Forming Silver Catalytic Sites from Silver-PhosphiteCarboxylates” (Attorney Docket K001835/JLT);

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla andDonovan) entitled “Forming Silver Catalytic Sites from ReducibleSilver-Oximes” (Attorney Docket K001836/JLT);

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla) entitled“Metal Catalytic Composition with Oxyazinium Photoreducing Agent”(Attorney Docket K001930/JLT);

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla) entitled“Metal Catalytic Composition with SilverCarboxylate-Trialkyl(Triaryl)phosphite Complex” (Attorney DocketK001931/JLT);

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla) entitled“Metal Catalytic Composition with Silver-Oxime Complex” (Attorney DocketK001932/JLT); and

U.S. Ser. No. 14/______ (filed on even date herewith by Shukla) entitled“Metal Catalytic Composition with Silver N-Heterocycle Complex”(Attorney Docket K001933/JLT).

FIELD OF THE INVENTION

This invention relates to a method for forming silver particles in-situfrom reducible silver ions that are provided from a coating or patternof a non-aqueous metal catalytic composition containing a silver complexof a hindered aromatic N-heterocycle having reducible silver ions, asilver ion photoreducing composition, and a photocurable component ornon-curable polymer. The resulting silver particles in the layer orcoating can be used directly as electrically-conductive materials or as“seed” catalytic sites for electroless plating of a suitableelectrically-conductive metal.

BACKGROUND OF THE INVENTION

Rapid advances are occurring in various electronic devices especiallydisplay devices that are used for various communicational, financial,and archival purposes. For such uses as touch screen panels,electrochromic devices, light emitting diodes, field effect transistors,and liquid crystal displays, conductive films are essential andconsiderable efforts are being made in the industry to improve theproperties of those conductive films.

There is a particular need to provide touch screen displays and devicesthat contain improved conductive film elements. Currently, touch screendisplays use Indium Tin Oxide (ITO) coatings to create arrays ofcapacitive areas used to distinguish multiple point contacts. ITOcoatings have significant short comings. Indium is an expensive rareearth metal and is available in limited supply from very few sources inthe world. ITO conductivity is relatively low and requires short linelengths to achieve adequate response rates. Touch screens for largedisplays are broken up into smaller segments to reduce the conductiveline length to an acceptable resistance. These smaller segments requireadditional driving and sensing electronics. In addition ITO is a ceramicmaterial, is not readily bent or flexed, and requires vacuum depositionwith high processing temperatures to prepare the conductive layers.

Silver is an ideal conductor having conductivity 50 to 100 times greaterthan ITO. Silver is used in many commercial applications and isavailable from numerous sources. It is highly desirable to makeconductive film elements using silver as the source of conductivity.

Numerous publications describe the preparation ofelectrically-conductive films formed by reducing a silver halide imagein silver halide emulsions in the form of electrically-conductive gridnetworks having silver wires having sizes of less than 10 μm. Variousefforts have been made to design the silver halide emulsions andprocessing conditions to optimize such electrically-conductive gridnetworks and the methods for making them.

For example, improvements have been proposed for providingelectrically-conductive grid patterns from silver halides by optimizingthe silver halide emulsions as well as finding optimized processingsolutions and conditions to convert latent silver images into silvermetal grid patterns. The precursors used to provide the conductive filmscan comprise one or more silver halide emulsion layers on opposing sidesof a transparent substrate, along with optional filter layers andhydrophilic overcoats.

While these processes and articles can provide desiredelectrically-conductive films, optimizing the design of both theprecursors and processing procedures requires considerable effort inorder to achieve the exacting features required inelectrically-conductive films to be incorporated into touch screendisplays.

Other industrial approaches to preparing electrically-conductive filmsor elements have been directed to formulating and applying photocurablecompositions containing dispersions of metal particles such as silvermetal particles to substrates, followed by curing of the photocurablecomponents in the photocurable compositions. The applied silverparticles thus act as catalytic (seed) particles for electrolesslyplated electrically-conductive metals. Useful electrically-conductivegrids prepared in this manner are described for example in WO2013/063183 (Petcavich), WO 2013/169345 (Ramakrishnan et al.). Otherdetails of a useful manufacturing system for preparing conductivearticles especially in a roll-to-roll manner are provided inPCT/US/062366 (filed Oct. 29, 2012 by Petcavich and Jin).

Using these methods, photocurable compositions containing silverparticles can be printed and cured on a suitable transparent substratefor example a continuous roll of a transparent polyester, and thenelectroless plating can be carried out. These methods require that highquantities of silver particles be dispersed within the photocurablecompositions in a uniform manner so that coatings or printed patternshave sufficiently high concentration of catalytic sites. This generallycannot be achieved without carefully designed dispersants and dispersingprocedures and such dispersants can be expensive and hard to use in amanner to provide reproducible products in a high speed manufacturingoperation. Without effective dispersing, silver particles can readilyagglomerate, leading to less effective and uniform application ofcatalytic metal patterns and electroless plating. It is thereforedifficult to provide uniform electrically-conductive films having thedesired electrically-conductive metal patterns.

U.S. Patent Application Publication 2007/0261595 (Johnson et al.)describes a method for electroless deposition on a substrate that usesan ink composition containing silver as a reducible silver salt andfiller particles. After reducing the reducible silver ions, suchcompositions can be cured for improved adhesion to the substrateespecially if the compositions contain an UV-curable monomer oroligomer.

U.S. Pat. No. 7,875,416 (Park et al.) describes photosensitivecompositions comprising a multifunctional epoxy resin, a photoacidgenerator, an organic solvent, and silver particles.

A common coordinating ion to form organic silver complexes is carboxylicacid [Prog. Inorg. Chem., 10, 233 (1968)]. However, silver-carboxylatecomplexes are generally sensitive to light and hardly soluble in organicsolvents [U.S. Pat. No. 5,491,059 of Whitcomb and U.S. Pat. No.5,534,312 of Hill et al.] and have a high decomposition temperature.Thus, such complexes have little utility in spite of ready availability.To solve this problem, several methods have been proposed for example,in Ang. Chem., Int. Ed. Engl., 31, p. 770 (1992), Chem. VaporDeposition, 7, 111 (2001), Chem. Mater., 16, 2021 (2004), and U.S. Pat.No. 5,705,661 (Iwakura et al.). Among such methods are those usingcarboxylic acid compounds having long alkyl chains or including aminecompounds or phosphine compounds. However, the silver derivatives knownthus far are limited and have insufficient stability or solubility.Moreover, they have a high decomposition temperature needed to be usefulfor pattern formation and are decomposed slowly.

U.S. Pat. No. 7,682,774 (Kim et al.) describes other photosensitivecompositions comprising silver fluoride organic complex precursors ascatalyst precursors. This patent describes the use of polymer derivedfrom a monomer having a carboxyl group and a co-polymerizable monomerthat may provide polymeric stability and developability of the resulting“seed” silver catalyst particles used for electroless plating.

Despite the various techniques described in the art, there remains aneed for an improved means for providing silver catalytic (seed)particles for electroless plating in the formation ofelectrically-conductive patterns in a reproducible and high-speed mannersuitable for continuous high-speed production. It is particularlydesirable to provide a method for high-speed production ofelectrically-conductive patterns without the need for complicated anduncertain dispersing procedures for high concentrations of silver metalparticles.

SUMMARY OF THE INVENTION

The present invention provides a method for providing an article, themethod comprising:

providing a metal catalytic layer or a metal catalytic pattern composedof a non-aqueous metal catalytic composition on a substrate, thenon-aqueous metal catalytic composition comprising:

(a) a complex of silver and a hindered aromatic N-heterocycle comprisingreducible silver ions, in an amount of at least 2 weight %,

(b) a silver ion photoreducing composition in an amount of at least 1weight %, and

(c) a photocurable component, a non-curable polymer, or a combination ofa photocurable component and a non-curable polymer,

all amounts being based on the total amount of components (a) through(c) in the non-aqueous metal catalytic composition,

to provide a precursor article comprising the metal catalytic layer orthe metal catalytic pattern composed of the non-aqueous metal catalyticcomposition.

In some embodiments, the method can further comprise:

photoreducing the reducible silver ions to silver particles in the metalcatalytic layer or the metal catalytic pattern.

In some embodiments, the method further comprises, after photoreducingthe reducible silver ions to silver particles:

electrolessly plating a metal other than silver onto the silverparticles in the metal catalytic layer or metal catalytic pattern.

The advantage of the present invention is to provide a source of silverparticles that can be used as electrically-conductive silver metal orcatalytic (seed) sites for electroplating without having to dispersesilver particles in various photocurable compositions. The presentinvention avoids the need to carefully disperse silver particles andpotential agglomeration in coating or printing compositions (“inks”) by“creating” or generating the silver particles in-situ as seed catalystsafter a photocurable composition has been coated or printed. Thus, thesilver particles are generated “in situ” from reducible silver ions thatcan be provided in silver complexes in coated or printed metal catalyticcompositions. Using this means for producing silver metal particlesreduces possible operator errors during dispersing processes and reducesdefects in producing electrically-conductive patterns. These advantagesare particularly useful in high-speed manufacturing operations such asroll-to-roll methods in which the application, curing, and electrolessplating can be carried out in a continuous manner.

Thus, important differences between the present invention and what isknown in the art include at least the following:

1) A number of silver containing complexes are known but whereformulations are to be designed with high concentrations of pre-formedsilver particles, such as loaded pastes and inks, the formulationsbecome highly complex in order to make them stable as dispersions of thesilver particles. The present invention avoids this problem by enablingthe formation of high concentrations of silver particles for variousphotocurable compositions (that is, non-aqueous metal catalyticcompositions).

2) Photochemical methods used to generate silver nanoparticles usesilver nitrate and methyl diethanolamine that are starting materialsthat show poor stability (that is, the silver ions are reducedthermally) and cause gelling of polymerizable monomers by the silverions. The present invention avoids this problem by forming silverparticles in situ and avoids the use of unstable reactants.

3) Known photochemical methods used to generate silver nanoparticleshave little practical utility as they use silver nitrate as a startingmaterial and this salt exhibits poor shelf keeping or dark stability.The present invention avoids this problem by using silver complexes inphotocurable compositions (that is, non-aqueous metal catalyticcompositions) that are light stable precursors for photogeneratingsilver particles in thin films or other useful formats.

4) Other known photochemical methods used to generate silvernanoparticles use silver fluoride organic complex precursors as catalystprecursors. For example, U.S. Pat. No. 7,682,774 (noted above) describesthe use of a carboxyl group containing polymer that has an acid value of90 to 700 mg KOH/g. The described process additionally requires first aheating at 100° C., reduction of the silver fluoride complex, and thenelectroless plating. The present invention provides a much simplerprocess and is not restricted to carboxyl-containing polymers andoligomers that exhibit various problems described above.

5) Known compositions containing silver nanoparticles generally containligands or dispersing agent that provide only stabilization orsolubilization of the particles. The present invention avoids this byproviding stabilized silver complexes in non-aqueous metal catalyticcompositions that provide an easy way to generate silver particleswithout the need for separate stabilizing ligands or dispersing agents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the crystal structure of a silver complexprepared for the examples below.

FIG. 2 is an illustration of the crystal structure of a silver complexprepared for the examples below.

FIG. 3 is an illustration of the crystal structure of a silver complexprepared for the examples below.

FIG. 4 shows absorption spectra showing silver plasmon band formationupon in situ photogeneration of silver nanoparticles using the silvercomplex prepared in Invention Example 2 below.

FIG. 5 is a micrograph of an article prepared according to the presentinvention in Invention Example 3 below.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered to limit the scope of the present invention, asclaimed below. In addition, one skilled in the art will understand thatthe following disclosure has broader application than is explicitlydescribed with the discussion of any one embodiment.

DEFINITIONS

As used herein to define the essential and optional components of thevarious non-aqueous metal catalytic compositions, unless otherwiseindicated, the singular forms “a,” “an,” and “the” are intended toinclude one or more of the components (that is, including pluralityreferents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the termdefinition should be taken from a standard dictionary or have customaryor commonly understood meaning.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated otherwise, are considered to beapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about”. In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

Unless otherwise indicated, the term “weight %” refers to the amount ofa component or material based on the total solids of a non-aqueous metalcatalytic composition, formulation, solution, or the % of the dry weightof a metal catalytic layer or metal catalytic pattern. Unless otherwiseindicated, the percentages can be the same for either a dry metalcatalytic layer or metal catalytic pattern, or for the total solids ofthe formulation or non-aqueous metal catalytic composition used to makethat metal catalytic layer or metal catalytic pattern.

As used herein, the terms “curing” and “photocuring” mean thepolymerization of functional oligomers and monomers, or even polymers,into a crosslinked polymer network as initiated by suitable irradiation.Curing can be polymerization of unsaturated monomers or oligomers asphotocurable components in the presence of crosslinking agents.

The photocurable components can be photocured when irradiated withsuitable radiation, for example ultraviolet (UV) or visible radiationhaving a wavelength of at least 150 nm and up to and including 750 nm.

Unless otherwise indicated, the terms “non-aqueous metal catalyticcomposition” and “metal catalytic composition” are considered to be thesame.

Unless otherwise indicated, the term “non-aqueous” as applied to themetal catalytic composition means that liquids in such compositions arepredominantly organic solvents and water is not purposely added and ispresent in an amount of less than 10 weight %, or particular of lessthan 5 weight %, or even less than 1 weight %, of the total non-aqueousmetal catalytic composition weight. In most instances, the presence ofwater can adversely affect the silver complexes used in the presentinvention and is not present at all (less than 0.0001 weight %).

Average dry thickness of metal catalytic layers or metal catalyticpatterns described herein can be the average of at least 2 separatemeasurements taken, for example, using electron microscopy.

Similarly, the average dry thickness or width of lines, grid lines, orother pattern features described herein can be the average of at least 2separate measurements taken, for example, using electron microscopy.

Unless otherwise indicated, the term “group” particularly when used todefine a substituent of a define moiety, can itself be substituted orunsubstituted (for example and alkyl group” refers to a substituted orunsubstituted alkyl). Generally, unless otherwise specifically stated,substituents on any “groups” referenced herein or where something isstated to be possibly substituted, include the possibility of anygroups, whether substituted or unsubstituted, which do not destroyproperties necessary for the utility of the component or non-aqueousmetal catalytic composition. It will also be understood for thisdisclosure and claims that reference to a compound of a particulargeneral structure includes those compounds of other more specificformula that fall within the general structural definition. Examples ofsubstituents on any of the mentioned groups can include knownsubstituents such as: halogen (for example, chloro, fluoro, bromo, andiodo); alkoxy particularly those with 1 to 12 carbon atoms (for example,methoxy and ethoxy); substituted or unsubstituted alkyl groups,particularly lower alkyl groups (for example, methyl andtrifluoromethyl); alkenyl or thioalkyl (for example, methylthio andethylthio), particularly either of those with 1 to 12 carbon atoms;substituted and unsubstituted aryl, particularly those having from 6 to20 carbon atoms in the aromatic ring (for example, phenyl); andsubstituted or unsubstituted heteroaryl, particularly those having a 5-or 6-membered ring containing 1 to 3 heteroatoms selected from N, O, Sor Se (for example, pyridyl, thienyl, furyl, pyrrolyl, and theircorresponding benzo and naptho analogs); and other substituents thatwould be readily apparent in the art. Alkyl substituents particularlycontain 1 to 12 carbon atoms and specifically include “lower alkyl” thatis having from 1 to 6 carbon atoms, for example, methyl, ethyl, andt-butyl. Further, with regard to any alkyl group, alkylene group oralkenyl group, it will be understood that these can be branched orunbranched and include ring (cyclic) structures.

Uses

The non-aqueous metal catalytic compositions can be used for a varietyof purposes where efficient photocuring or photopolymerization is neededin various articles or devices. Such non-aqueous metal catalyticcompositions are sensitive to a chosen radiation wavelength as notedabove. For example, the non-aqueous metal catalytic compositions can beused to provide electrically-conductive metal patterns, for exampleusing electroless plating procedures that can be incorporated intovarious devices including but not limited to touch screen or othertransparent display devices that can be used in numerous industrial andcommercial products.

For example, touch screen technology can comprise different touch sensorconfigurations including capacitive and resistive touch sensors.Resistive touch sensors comprise several layers that face each otherwith a gap between adjacent layers that may be preserved by spacersformed during manufacturing. A resistive touch screen panel can compriseseveral layers including two thin, metallic, electrically-conductivelayers separated by a gap that can be created by spacers. When an objectsuch as a stylus, palm, or fingertip presses down on a point on thepanel's outer surface, the two metallic layers come into contact and aconnection is formed that causes a change in the electrical current.This touch event is sent to a controller for further processing.

Capacitive touch sensors can be used in electronic devices withtouch-sensitive features. These electronic devices can include but arenot limited to, televisions, monitors, and projectors that can beadapted to display images including text, graphics, video images,movies, still images, and presentations. The image devices that can beused for these display devices that can include cathode ray tubes(CRS's), projectors, flat panel liquid crystal displays (LCD's), LEDsystems, OLED systems, plasma systems, electroluminescent displays(ECD's), and field emission displays (FED's). For example, the presentinvention can be used to prepare capacitive touch sensors that can beincorporated into electronic devices with touch-sensitive features toprovide computing devices, computer displays, portable media playersincluding e-readers, mobile telephones and other communicating devices.

Systems and methods of fabricating flexible and optically complianttouch sensors in a high-volume roll-to-roll manufacturing process wheremicro electrically-conductive features can be created in a single passare possible using the present invention. The non-aqueous metalcatalytic compositions can be used in such systems and methods byapplication with printing members such as flexographic printing plates.Multiple patterns of non-aqueous metal catalytic compositions can beprinted on one or both sides of a substrate as described in more detailsbelow. For example, one predetermined pattern can be printed on one sideof the substrate and a different predetermined pattern can be printed onthe opposing side of the substrate. The printed patterns of thenon-aqueous metal catalytic compositions can then be further processedto provide electrically-conductive metal patterns using, for exampleelectroless metal plating.

Non-Aqueous Metal Catalytic Compositions

In general, the non-aqueous metal catalytic compositions describedherein are sensitive throughout the UV to visible spectral region asdescribed above and are photocurable without appreciable application ofheat. Thus, photocuring can occur at essentially room temperature (forexample, as low as 18° C.) when all of the components of the non-aqueousmetal catalytic compositions are properly mixed together. Thenon-aqueous metal catalytic compositions are designed to be effectivewhen they comprise the essential components described herein, which arethe only components necessary to achieve the desired efficientphotocuring. Optional addenda can also be included as described below.

The non-aqueous metal catalytic composition useful in the presentinvention comprises three essential components (a) through (c) andpossible optional components as described below.

The essential component (a) includes one or more complexes of silver andhindered aromatic N-heterocycle comprising reducible silver ions.Recrystallisation of silver halides from neat nitrogen-containing basesproduces crystalline products mostly of 1:1 silver halide:nitrogen basestoichiometry [Coord. Chem. Rev., 253 (2009) 325-342]. Silver complexeswith nitrogen-containing ligands are featured prominently as the organicbuilding blocks [for example, see Coord. Chem. Rev., 222 (2001), p.155]. In particular, multifunctional pyridine ligands are widelyemployed for the generation of intriguing supramolecular architectures.Interaction of silver with simple pyridines is known (see for example,J. Inorg. Nucl. Chem., 34, 1972, 2987) but no such complexes have beenisolated.

The term “hindered” used to define hindered aromatic N-heterocycle meansthat the moiety has a “bulky” group that is located in the a position tothe nitrogen atom in the aromatic ring. Such bulky groups can be definedusing the known “A-value” parameter that is a numerical value used forthe determination of the most stable orientation of atoms in a molecule(using conformational analysis) as well as a general representation ofsteric bulk. A-values are derived from energy measurements of amono-substituted cyclohexane ring. Substituents on a cyclohexane ringprefer to reside in the equatorial position to the axial. The differencein Gibbs free energy between the higher energy conformation (axialsubstitution) and the lower energy conformation (equatorialsubstitution) is the A-value for a particular substituent (see forexample, Eliel et al., Stereochemistry of Organic Compounds, Wiley,1993, p. 696; and White et al. J. Org. Chem. 1999, 64, 7707-7716).

In the present invention, the useful “bulky” groups in the hinderedaromatic N-heterocycle have an A-value of at least 05.

Some silver complexes with hindered aromatic N-heterocycle useful in thepresent invention can be defined using the following nitrogen containingligands of following structure:

[Ag_(a)(L)_(b)](X)_(a)

wherein a is 1 or 2; b is 1, 2, or 3;

L is a hindered aromatic N-heterocycle; and

X is a coordinating or non-coordinating anion such as NO₃ ⁻, ClO₄ ⁻, BF₄⁻, SbF₆ ⁻, PF₆ ⁻, CH₃SO₃ ⁻, or F₃CSO₃ ⁻.

Examples of some complexing hindered nitrogen-containing aromaticheterocycles are as follows:

Silver complexes with oxazoline-containing bidentate ligands are known[see for example, Inorg. Chim. Acta 392 (2012) 38-45] and are useful ascomponent (a) in present invention.

In some embodiments, such silver complexes used in the present inventioncan have the following structure:

wherein n is 1 to 4; m is 1 to 4; p is 1 to 4; q is 1 to 4;

X is a coordinating or non-coordinating anion such as NO₃ ⁻, ClO₄ ⁻, BF₄⁻, SbF₆ ⁻, PF₆ ⁻, CH₃SO₃, or F₃CSO₃ ⁻;

R_(b) and R_(c) are independently H or a substituted or unsubstitutedalkyl group or a substituted or unsubstituted aryl group; and

R_(a) and R_(d) are independently —COOR_(e), —CONR_(f)R_(g), —CHO, —CN,—SO₂ wherein R_(e), R_(f), and R_(g) are independently a substituted orunsubstituted alkyl group (linear, branched, or cyclic) having 1 to 12carbon atoms, or a substituted or unsubstituted aryl groups.

Representative useful component (a) complexes are one or more of thefollowing AgPy-1 through AgPy-9:

The silver complexes described above can be at least partially solublein the inert organic solvents that can be present in the metal catalyticcomposition in order to achieve dispersion of all components. In someembodiments, the silver complex can be soluble in the photocurablecomponents that can be present in the non-aqueous metal catalyticcomposition. Conveniently, finely solid dispersions of insoluble silvercomplexes can also be present. Alternatively, the silver complex can beadded to an inert organic solvent before being mixed with photocurablecomponents to aid the transfer or mixing of the silver complex in theresulting non-aqueous metal catalytic composition.

Some additional useful component (a) silver hindered aromaticN-heterocycle complexes include but not limited to, silver-benzthiazolecomplexes, silver-pyrimidine complexes, silver-pyrazine complexes, andsilver benzoxazole complexes. Mixtures of such silver complexes can beused if desired.

The described silver complexes can be prepared using procedures thatwould be readily apparent to one skilled in the art especially in viewof the teaching of preparatory methods provided for the Examples below.

These essential component (a) of silver complexed with a hinderedaromatic N-heterocycle comprising reducible silver ions can be presentin the non-aqueous metal catalytic composition in an amount of at least2 weight % and up to and including 90 weight %, and typically in anamount of at least 2 weight % and up to and including 25 weight %, allbased on the total amount of components (a) through (c) in thenon-aqueous metal catalytic composition.

The non-aqueous metal catalytic composition also includes a component(b) silver ion photoreducing composition that comprises one or moredifferent compounds that upon photoexposure reduce the silver ions.

For example, in one embodiment, the silver ion photoreducing compositioncan comprise one or more known electron rich triplet photosensitizers.In general, many different classes of compounds can be used as tripletphotosensitizers including but not limited to, aromatics such asnaphthalene, 1-methylnaphthalene, anthracene, 9,10-dimethoxyanthracene,benz[a]anthracene, pyrene, phenanthrene, benzo[c]phenanthrene, andfluoranthene; thioxanthones and xanthones; ketones including aromaticketones such as fluorenone, and coumarin dyes such as ketocoumarins suchas those with strong electron donating moieties (such as dialkylamino).Other suitable electron donor photosensitizers include xanthene dyes,acridine dyes, thiazole dyes, thiazine dyes, oxazine dyes, azine dyes,aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons,p-substituted aminostyryl ketone compounds, aminotriarylmethanes,merocyanines, squarylium dyes, and pyridinium dyes.

In still other embodiments, useful triplet photosensitizers include butare not limited to, ketocoumarins, xanthones, thioxanthones,arylketones, and polycyclic aromatic hydrocarbons in amounts describedabove.

As used herein, oxidation potentials are reported as “V” that represents“volts versus a saturated calomel reference electrode”.

In most embodiments of this invention, the non-aqueous metal catalyticcomposition comprises one or more component (b) silver ion photoreducingcomposition comprising one or more compounds defined as X—Y compoundswherein X is an electron donor moiety and Y is a leaving group otherthan hydrogen, and further wherein:

1) Upon absorption of light, the X—Y compound undergoes a bond cleavagereaction to give the radical X. and the leaving fragment Y. and radicalX. has an oxidation potential ≦−0.2V (that is, equal to or more negativethan about −0.2V).

2) Upon energy transfer from a photosensitizer (described below) thatcan be present, the X—Y compound undergoes a bond cleavage reaction togive the radical X. and the leaving fragment Y., and radical X. has anoxidation potential ≦−0.2V (that is, equal to or more negative thanabout −0.2V).

3) Upon electron transfer to a photosensitizer (described below), theX—Y compound undergoes electron transfer and bond cleavage reaction togive the radical X. and the leaving fragment Y⁺, and radical X. has anoxidation potential ≦−0.2V (that is, equal to or more negative thanabout −0.2V).

The structural features of the X—Y compound are defined by thecharacteristics of the two parts, namely electron donor moiety X andleaving group Y. The structural features of electron donor moiety Xdetermine the oxidation potential of the X—Y compound and that ofradical X., whereas both the X and Y fragments affect the fragmentationof the X—Y compound.

R used herein represents a hydrogen atom or an unsubstituted orsubstituted alkyl group (linear, branched, or cyclic groups) having 1 to12 carbon atoms. Moreover, R can be defined as the noted alkyl group,hydrogen (H), R₁, or R₂ as defined below.

Particularly useful X electron donor moieties can be represented by thefollowing Structure (I):

In Structure (I), m is 0 or 1;

-   -   Z is O, S, Se, or Te;

Ar is a carbocyclic aryl group (such as a substituted or unsubstitutedphenyl, naphthyl, phenanthryl, or anthryl group); heterocyclic group(such as a substituted or unsubstituted pyridine, indole, benzimidazole,thiazole, benzothiazole, or thiadiazole group); or cycloalkyl group(such as a substituted or unsubstituted cyclohexane or cyclopentanegroups);

R₁ is R, carboxyl, amide, sulfonamide, halogen, N(R)₂, (OH)_(n),(OR′)_(n), or (SR)_(n) wherein R′ is an substituted or unsubstitutedalkyl group and n is an integer of 1 to 3;

R₂ and R₃ are independently R or Ar′; or R₂ and R₃ together can form 5-to 8-membered ring; and independently each of R₂ and R₃ with Ar′ can belinked to form 5- to 8-membered substituted or unsubstituted ring; and

Ar′ is a substituted or unsubstituted aryl group including but notlimited to phenyl or substituted phenyl, or a substituted orunsubstituted heterocyclic group (such as pyridine or benzothiazole).

Other useful X electron donor moieties can be represented by thefollowing Structure (II):

-   -   wherein Ar is a substituted or unsubstituted aryl group (such as        phenyl, naphthyl, or phenanthryl group), or a substituted or        unsubstituted heterocyclic group (such as pyridine or        benzothiazole);    -   n is 0 or a positive integer of from 1 to 4;    -   R₄ is a substituent having a Hammett sigma value of from −1 and        up to and including +1, or typically of from −0.7 and up to and        including +0.7, including but not limited to R, OR, SR, halogen,        CHO, C(O)R, COOR, CON(R)₂, SO₃R, SO₂NR₂, SO₂R, SOR, C(S)R,        wherein R is are defined above;    -   R₅ is R or Ar′ as defined above;    -   R₆ and R₇ are independently R or Ar′ as defined above; or R₅ and        Ar′ can be linked to form 5- to 8-membered ring or R₆ and Ar′        can be linked to form 5- to 8-membered ring (in which case, R₆        can be a hetero atom); or R₅ and R₆ can be linked to form 5- to        8-membered ring; or R₆ and R₇ can be linked to form 5- to        8-membered ring; and    -   Ar′ is as defined above.

A discussion about Hammett sigma values can be found in C. Hansch and R.W. Taft, Chem. Rev. Vol 91, (1991) p 165.

Still other useful X electron donor moieties are defined by thefollowing Structure (III):

wherein in structure (III) Ar, n, and R₄ are as defined above exceptthat R₄ can also be morpholine.

Additional X electron donor moieties can be defined by the followingStructure (IV):

wherein W is O, S, or Se;

R and Ar are as defined above;

R₈ is R, carboxyl, N(R)₂, (OR)_(n), or (SR)_(n) (wherein n is 1 to 3);and

R₉ and R₁₀ are independently R or, Ar; or R₉ and Ar′ can be linked toform 5- to 8-membered ring; or Ar′ is a substituted or unsubstitutedaryl group as defined above.

Since X is an electron donor moiety (that is, an electron rich organicmoiety), the substituents on the aromatic groups (Ar and Ar′), for anyparticular X group should be selected so that X remains electron rich.For example, if the aromatic group is highly electron rich, such as ananthracene, electron withdrawing substituents can be used, providing theresulting X—Y compound has an oxidation potential greater than 1 V sothat no reduction of silver takes place without light. Conversely, ifthe aromatic group is not electron rich, electron donating substituentsshould be selected.

The following are illustrative examples of the X electron donor moietiesuseful in the present invention (wherein R is as defined above and n is1 to 3):

Structure (I) Structure (II) Structure (III) Structure (IV)

Particularly useful Y groups for the X—Y compounds include thefollowing:

wherein R₁₂ is R, carboxyl, N(R)₂, (OR)_(n), or (SR)_(n), wherein R isdefined above and n is 1 to 3.

Particularly useful X—Y compounds that fragment either by directabsorption of light or by energy transfer to generate a reducing radicalare S1 through S9 shown as follows:

The X—Y compound can be fragmented if it meets following criteria:

1) The first criterion relates to the photo-fragmentation quantum yieldof X—Y. Photo fragmentation yield the X—Y compound is desirably close to100%.

2) The second criterion relates to the sensitized fragmentation of theX—Y compound. For sensitized fragmentation of the X—Y compound, it isdesirable that the photosensitizer used has high triplet formation yieldand triplet energy E_(T). For example, the triplet energy (E_(T)) ofphotosensitizer can be higher than 50 kcal/mol.

3) The third criterion relates to the oxidative fragmentation of the X—Ycompound (E₁). For oxidative fragmentation, it is desirable to have anoxidation potential E₁ of the X—Y compound no higher than about 1.4 Vand less than about 1.0 V. The oxidation potential is desirably greaterthan 0, or greater than about 0.3 V. E₁ is desirably in the range of atleast 0 and up to and including 1.4 V, and or at least 0.3 V and up toand including 1.0 V.

One electron oxidation the X—Y compound to generate X—Y⁺. involvesfragmentation of X—Y⁺. and generates radical X. that reduces silver ionand Y is a leaving group (other than hydrogen). To achieve oxidativefragmentation, the following three conditions have to be met:

1) The X—Y compound has an oxidation potential at least 0 and up to andincluding 1.4 V.

2) The oxidized form of the X—Y compound undergoes a bond cleavagereaction to give the radical X. and the leaving fragment Y.

3) The radical X. has an oxidation potential ≦−0.2V (that is, equal toor more negative than about −0.2V).

X—Y compounds that meet criteria (1) and (2) but not criterion (3) arecapable of donating one electron and are referred to herein asfragmentable one-electron donor compounds. Compounds that meet all threecriteria are capable of donating two electrons and are referred toherein as fragmentable two-electron donor compounds. X—Y compounds thatfragment upon oxidation to generate silver ion reducing radicals havebeen disclosed in U.S. Pat. No. 5,747,236 (Farid et al.), the disclosureof which is incorporated herein in its entirety by reference.

In particularly useful embodiments of this invention, the X—Y compoundsthat fragment upon oxidation to generate reducing radical are defined byStructures (I), (II), or (IV) above. In these structures since X is anelectron donor moiety (that is, an electron rich organic group), thesubstituents on the aromatic groups (Ar and Ar′) for any particular Xelectron donor moiety should be selected so that X remains electronrich. For example, if the aromatic group is highly electron rich (forexample anthracene) electron withdrawing substituents can be used,providing the resulting the X—Y compound has an oxidation potential ofat least 0 and up to and including 1.4 V. Conversely, if the aromaticgroup is not electron rich, electron donating substituents should beselected.

One criterion defining the silver ion photoreducing compositions usefulin the present invention is the requirement that the oxidized form ofthe X—Y compound, that is the radical cation X—Y⁺., undergoes a bondcleavage reaction, other than deprotonation, to give the radical X. andthe neutral fragment Y⁺ (or in the case of an anionic compound theradical X. and the fragment Y). This bond cleavage reaction is alsoreferred to herein as “fragmentation”. It is widely known that radicalspecies, and in particular radical cations, formed by a one-electronoxidation reaction can undergo a multitude of reactions, some of whichare dependent upon their concentration and upon the specific environmentwherein they are produced (as described in “Kinetics and Mechanisms ofReactions of Organic Cation Radicals in Solution”, Advances in PhysicalOrganic Chemistry, vol 20, 1984, pp 55-180, and “Formation, Propertiesand Reactions of Cation Radicals in Solution”, Advances in PhysicalOrganic Chemistry, vol 13, 1976, pp 156-264, V. Gold Editor, 1984,published by Academic Press, N.Y.), and the range of reactions availableto such radical species includes dimerization, deprotonation,nucleophilic substitution, disproportionation, and bond cleavage. Withthe silver ion photoreducing compositions useful in the presentinvention, the oxidized form of the X—Y compound undergoes a bondcleavage reaction.

In particularly useful embodiments of the invention, the X—Y compound isa fragmentable two-electron donor and meets a third criterion, that is,the radical X. resulting from the bond cleavage reaction has anoxidation potential equal to or more negative than −0.2V, or typicallymore negative than about −0.7 V. This oxidation potential can be in therange of from at least −0.2 V and up to and including −2 V, ore moretypically at least −0.7 and up to and including −2 V or even at least−0.9 and up to and including −1.6 V.

Oxidation potentials of many useful X—Y compounds are well known and canbe found, for example, in Encyclopedia of Electrochemistry of theElements, Organic Section, Volumes XI-XV, A. Bard and H. Lund (Editors)Marcel Dekkar Inc., N.Y. (1984). E₁ can be measured by the technique ofcyclic voltammetry wherein the electron donor is dissolved in a solutionof 80%/20% by volume acetonitrile to water containing 0.1 molar lithiumperchlorate. Oxygen is removed from the solution by passing nitrogen gasthrough the solution for 10 minutes prior to measurement. A glassycarbon disk is used for the working electrode, a platinum wire is usedfor the counter electrode, and a saturated calomel electrode (SCE) isused for the reference electrode. Measurement is conducted at 25° C.using a potential sweep rate of 0.1 V/sec.

The kinetics of the bond cleavage or fragmentation reaction can bemeasured by conventional laser flash photolysis. The general techniqueof laser flash photolysis as a method to study properties of transientspecies is well known (see, for example, Absorption Spectroscopy ofTransient Species W. Herkstroeter and I. R. Gould in Physical Methods ofChemistry Series, second Edition, Volume 8, page 225, edited by B.Rossiter and R. Baetzold, John Wiley & Sons, New York, 1993).

The oxidation potential of many radicals have been measured by transientelectrochemical and pulse radiolysis techniques as reported by Wayner etal. in J. Am. Chem. Soc. 1988, 110, 132; Rao et al. in J. Am. Chem. Soc.1974, 96, 1287, Rao et al. in J. Am. Chem. Soc. 1974, 96, 1295, andGould et al. in J. Am. Chem. Soc. 2000,122, 11934. The data demonstratethat the oxidation potentials of tertiary radicals are less positive(that is, the radicals are stronger reducing agents) than those of thecorresponding secondary radicals, which in turn are more negative thanthose of the corresponding primary radicals. For example, the oxidationpotential of a benzyl radical decreases from 0.73V to 0.37 V and thendecreases to 0.16 V upon replacement of one or both hydrogen atoms bymethyl groups.

Some useful X—Y compounds that fragment upon oxidation to generatesilver ion reducing radicals are shown in the following table withvarious defined radicals (R₂₃ is the same for all of the S2 and S3 X—Ycompounds shown below):

S1

R₁₇ R₁₈ R₁₉ CH₃ H H C₂H₅ OH H CH₃ CH₃ OH C₆H₅ OH C₆H₅ C₄H₉ OH C₄H₉ C₄H₉OCH₃ C₄H₉ S2

R₂₀ R₂₁ R₂₂ R₂₃ OCH₃ H H H CH₃ H H H OCH₃ H CH₃ H CH₃ CH₃ H H S3

R₂₀ R₂₂ R₂₄ R₂₁ OCH3 CH₃ H H H CH₃ H H CH₃ CH₂CO₂ ⁻ H H (C₄H₉)₄N⁺ CH₃CH₂CO₂ ⁻ CH₃ H (C₄H₉)₄N⁺ S5

S6

S7

S8

The oxidation potential of many of such X—Y compounds have been reportedin U.S. Pat. No. 5,747,236 (noted above).

To activate oxidative fragmentation of an X—Y compound into anelectron-accepting photo sensitizer component, upon absorption of lightshould oxidize X—Y by electron transfer reaction, called photoinducedelectron transfer, to form X..

An electron-accepting photosensitizer compound useful in the silver ionphotoreducing composition initiates the chemical transformation of theX—Y compound in response to suitable radiation. Thus, theelectron-accepting photosensitizer compound must be capable of oxidizingthe X—Y compound to a radical cation after the electron-acceptingphotosensitizer compound has absorbed light (that is, photo-inducedelectron transfer). Thus, in some embodiments, upon absorption ofappropriate actinic radiation, the electron-accepting photosensitizercompound is capable of accepting an electron from the X—Y compound.

To determine whether a compound is capable of acting as anelectron-accepting photosensitizer to oxidize the X—Y compound toprovide X. after the photosensitizer has absorbed light, reactionenergetics can be used. There are three controlling parameters inreaction energetics: (1) the excitation energy (E_(PS*)) of theelectron-accepting photosensitizer (PS); (2) the reduction potential(E_(PS) ^(red)) of the electron-accepting photosensitizer component(PS); and (3) the oxidation potential (E_(X—Y) ^(ox)) of the X—Ycompound that is an electron donor. For these reactions to beenergetically feasible, the energy of the excited state should be higheror only slightly lower than the energy stored in the primary product,the radical ion pair, (PS⁻.X—Y⁺.).

The excitation energy of the electron-accepting photosensitizer (PS) isconveniently determined from the midpoint of the normalized absorptionand emission spectrum of PS, if the reaction proceeds from the singletexcited state. However, if the reaction proceeds via the triplet state,then the triplet energy of PS should be used as the excitation energy.

The energy of the radical ion pair, E_(IP), is given by Equation 1below, wherein Δ is an energy increment that depends on the mediumpolarity and ranges from nearly zero in highly polar media to about 0.3eV in the least polar media. The oxidation (E_(R) ^(ox)) and reduction(E_(PS) ^(red)) potentials are readily obtained from conventionalelectrochemical measurements in polar solvents such as acetonitrile ormethylene chloride.

$\begin{matrix}{E_{IP} = {E_{X - Y}^{ox} - E_{PS}^{red} + \Delta}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Polymeric media tend to be low in dielectric constant, and as a resultwould not strongly solvate the radical ion pair. Thus, the energyincrement Δ in Equation 1 is expected to be near the maximum value, thatis, in the range of 0.2 eV to 0.3 eV. Thus, an electron-acceptingphotosensitizer (PS) with excitation energy equal to or larger than thedifference between the oxidation potential of the reactant and thereduction potential of the acceptor, (E_(R) ^(ox)−E_(PS) ^(red)), willsatisfy the energetic requirements of photoinitiating the reaction asdescribed in the following Equation 2:

$\begin{matrix}{E_{{PS}^{*}} \geq {E_{X - Y}^{ox} - E_{PS}^{red}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

It is more convenient to express the energetic requirements of theelectron-accepting photosensitizer (PS) relative to the donor in termsof a rearranged form of Equation 2 shown below as Equation 3:

$\begin{matrix}{{E_{{PS}^{*}} + E_{PS}^{red}} \geq E_{X - Y}^{ox}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

According to Equation 3, for the reaction to be energetically feasible,the algebraic sum of the excitation energy of the electron-acceptingphotosensitizer and its reduction potential should be approximatelyequal to or larger than the oxidation potential of the reactant.Numerous electron-accepting photosensitizers (PS) that meet therequirement of Equation 3, can be used.

Representative electron-accepting photosensitizers include but are notlimited to, cyano-substituted carbocyclic aromatic compounds orcyanoaromatic compounds (such as 1-cyanonaphthalene,1,4-dicyanonaphthalene, 9,10-dicyanoanthracene,2-t-butyl-9,10-dicyanoanthracene, 2,6-di-t-butyl-9,10-dicyanoanthracene,2,9,10-tricyanoanthracene, 2,6,9,10-tetracyanoanthracene), aromaticanhydrides and aromatic imides (such as 1,8-naphthylene dicarboxylic,1,4,6,8-naphthalene tetracarboxylic, 3,4-perylene dicarboxylic, and3,4,9,10-perylene tetracarboxylic anhydride or imide), condensedpyridinium salts (such as quinolinium, isoquinolinium, phenanthridinium,acridinium salts), and pyrylium salts. Useful electron-acceptingphotosensitizers that involve the triplet excited state include but arenot limited to, carbonyl compounds such as quinones (for example,benzo-, naphtho-, and anthro-quinones with electron withdrawingsubstituents such as chloro and cyano). Ketocoumarins especially thosewith strong electron withdrawing moieties such as pyridinium can also beused as electron-accepting photosensitizers. These compounds canoptionally contain substituents such as methyl, ethyl, tertiary butyl,phenyl, methoxy, and chloro groups that can be included to modifyproperties such as solubility, absorption spectrum, and reductionpotential. The electron-accepting photosensitizers used in the presentinvention can also be derived from the noted compounds.

Some compounds that meet the requirement of Equation 3 are listed asPS-1 through PS-18 below in the following Table.

PS-1

PS-2

PS-3

PS-4

PS-5

PS-6

PS-7

PS-8

PS-9

PS-10

PS-12

PS-13

PS-14

PS-15

PS-16

PS-17

PS-18

The silver ion photoreducing composition (comprising one or morecompounds such as X—Y compounds with or without electron-acceptingphotosensitizers PS) is present in the non-aqueous metal catalyticcomposition in an amount of at least 1 weight % and up to and including90 weight %, and typically in an amount of at least 2 weight % and up toand including 10 weight %, all based on the total amount of components(a) through (c) in the non-aqueous metal catalytic composition.

In addition, the non-aqueous metal catalytic composition comprisesessential component (c) that comprises one or more photocurablecomponents, one or more non-curable polymers, or a combination of one ormore photocurable components and one or more non-curable polymers.

Overall, the one or more photocurable components or the one or morenon-curable polymers can be present in the non-aqueous metal catalyticcomposition in a total amount of at least 10 weight % and up to andincluding 97 weight %, and typically at least 10 weight % and up to andincluding 50 weight %, all based on the total amount of essentialcomponents (a) through (c) in the non-aqueous metal catalyticcomposition. The amounts of each type of component (c) can be adjusteddepending upon what the material is designed to do and useful amounts ofspecific photocurable components and non-curable polymers are describedbelow. The amounts can also be adjusted when there are multiplematerials comprising the photocurable components, such as photocurablemonomers, oligomers, or polymers as well as photoinitiators that may beneeded with such materials.

The useful photocurable components are considered materials that canparticipate in a photocuring reaction, for example as a photocurablemonomer, oligomer, or polymer or as a photoinitiator or co-initiator.Such photocurable components can be designed to participate in eitherfree radical photocuring in which free radicals are generated uponphotoexposure, or in acid-catalyzed photocuring in which an acid isgenerated for reaction and curing of an epoxy compound.

In general, the photocurable components are sensitive throughout the UVto visible spectral region as described above and are photocurable orcause photocuring in these electromagnetic regions without appreciableapplication of heat. Thus, photocuring or photopolymerization can occurat essentially room temperature (for example, as low as 18° C.) when allof the components are properly mixed together.

Examples of photocurable components that participate in acid-catalyzedphotocuring including photopolymerizable epoxy materials that areorganic compounds having at least one oxirane ring that is polymerizableby a ring opening mechanism. Such epoxy materials, also called“epoxides”, include monomeric epoxy compounds and epoxides of thepolymeric type and can be aliphatic, cycloaliphatic, aromatic orheterocyclic. These materials generally have, on the average, at leastone polymerizable epoxy group per molecule, or typically at least about1.5 and even at least about 2 polymerizable epoxy groups per molecule.Polymeric epoxy materials include linear polymers having terminal epoxygroups (for example, a diglycidyl ether of a polyoxyalkylene glycol),polymers having skeletal (backbone) oxirane units (for example,polybutadiene polyepoxide), and polymers having pendant epoxy groups(for example, a glycidyl methacrylate polymer or copolymer).

The polymerizable epoxy materials can be single compounds or they can bemixtures of different epoxy materials containing one, two, or more epoxygroups per molecule. The “average” number of epoxy groups per moleculeis determined by dividing the total number of epoxy groups in the epoxymaterial by the total number of epoxy-containing molecules present.

The epoxy materials can vary from low molecular weight monomericmaterials to high molecular weight polymers and they can vary greatly inthe nature of the backbone and substituent (or pendant) groups. Forexample, the backbone can be of any type and substituent groups thereoncan be any group that does not substantially interfere with cationicphotocuring process desired at room temperature. Illustrative ofpermissible substituent groups include but are not limited to, halogens,ester groups, ethers, sulfonate groups, siloxane groups, nitro groups,and phosphate groups. The molecular weight of the epoxy materials can beat least 58 and up to and including 100,000, or even higher.

Specific useful epoxy materials would be readily apparent to one skilledin the art. Many commercially available epoxy materials are useful inthe present invention, glycidyl ethers such as bisphenol-A-diglycidylether (DGEBA), glycidyl ethers of bisphenol S and bisphenol F,butanediol diglycidyl ether, bisphenol-A-extended glycidyl ethers,phenol-formaldehyde glycidyl ethers (epoxy novolacs) andcresol-formaldehyde glycidyl ethers (epoxy cresol novolacs), epoxidizedalkenes such as 1,2-epoxyoctane, 1,2,13,14-tetradecane diepoxide,1,2,7,8-octane diepoxide, octadecylene oxide, epichlorohydrin, styreneoxide, vinyl cyclohexene oxicyclohexene oxide, glycidol, glycidylmethacrylate, diglycidyl ether of Bisphenol A (for example, thoseavailable under the EPON trademark such as EPON™ 828, EPON™ 825, EPON™1004, and EPON™ 1010 from Momentive, DER-331, DER-332, and DER-334resins from Dow Chemical Co.), vinyl cyclohexene dioxide (for example,ERL-4206 resin from Polyscience),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (for example,ERL-4221, UVR 6110, or UVR 6105 resin from Dow Chemical Company),3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methyl-cyclohexenecarboxylate (from Pfalz and Bauer),bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate,bis(2,3-epoxy-cyclopentyl) ether, aliphatic epoxy modified withpolypropylene glycol, dipentene dioxide, epoxidized polybutadiene (forexample, Oxiron 2001 resin from FMC Corp.), silicone resin containingepoxy functionality, flame retardant epoxy resins (for example, DER-580resin, a brominated bisphenol type epoxy resin available from DowChemical Co.), 1,4-butanediol diglycidyl ether of phenol formaldehydenovolak (for example, DEN-431 and DEN-438 resins from Dow Chemical Co.),resorcinol diglycidyl ether (for example, CYRACURE™ resin from DowCorning Corp.),2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane,2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane,vinyl cyclohexene monoxide, 1,2-epoxyhexadecane (for example, CYRACURE™resin from Dow Corning Corp.), alkyl glycidyl ethers such as HELOXY™Modifier 7 and HELOXY™ Modifier 8 (from Momentive), butyl glycidyl ether(for example, HELOXY™ Modifier 61 from Momentive), cresyl glycidyl ether(for example, HELOXY™ Modifier 62 from Momentive), p-tert butylphenylglycidyl ether (for example, HELOXY™ Modifier 65 from Momentive),polyfunctional glycidyl ethers such as diglycidyl ether of1,4-butanediol (for example, HELOXY™ Modifier 67 from Momentive),diglycidyl ether of neopentyl glycol (for example, HELOXY™ Modifier 68from Momentive), diglycidyl ether of cyclohexanedimethanol (for example,HELOXY™ Modifier 107 from Momentive), trimethylol ethane triglycidylether (for example, HELOXY™ Modifier 44 from Momentive), trimethylolpropane triglycidyl ether (for example, HELOXY™ Modifier 48 fromMomentive), polyglycidyl ether of an aliphatic polyol (for example,HELOXY™ Modifier 84 from Momentive), polyglycol diepoxide (for example,HELOXY™ Modifier 32 from Momentive), bisphenol F epoxides (for example,EPN-1138 or GY-281 resin from Huntman Advanced Materials), and9,9-bis>4-(2,3-epoxypropoxy)-phenyl fluorenone (for example, EPON™ 1079resin from Momentive).

Still other useful epoxy materials are resins such as copolymers derivedfrom acrylic acid esters reacted with glycidol such as glycidyl acrylateand glycidyl methacrylate, copolymerized with one or more ethylenicallyunsaturated polymerizable monomers. Examples of such copolymers arepoly(styrene-co-glycidyl methacrylate) (50:50 molar ratio), poly(methylmethacrylate-co-glycidyl acrylate) (50:50 molar ratio), and poly(methylmethacrylate-co-ethyl acrylate-co-glycidyl methacrylate) (62.5:24:13.5molar ratio).

One or more photopolymerizable epoxy materials can be included in thenon-aqueous metal catalytic composition in a suitable amount to providethe desired efficient photocuring or photopolymerization. For example,the one or more photopolymerizable epoxy materials can be present in anamount of at least 10 weight % and up to and including 50 weight %,based on the total amount of components (a) through (c) in thenon-aqueous metal catalytic composition.

Various compounds can be used to generate a suitable acid to participatein the photocuring of the photopolymerizable epoxy materials describedabove. Some of these “photoacid generators” are acidic in nature andothers are nonionic in nature. Other useful photoacid generators besidesthose described below would be readily apparent to one skilled in theart in view of the teaching provided herein. The various compoundsuseful as photoacid generators can be purchased from various commercialsources or prepared using known synthetic methods and startingmaterials.

Onium salt acid generators useful in the practice of this inventioninclude but are not limited to, salts of diazonium, phosphonium,iodonium, or sulfonium salts including polyaryl diazonium, phosphonium,iodonium, and sulfonium salts. The iodonium or sulfonium salts includebut not limited to, diaryliodonium and triarylsulfonium salts. Usefulcounter anions include but are not limited to complex metal halides,such as tetrafluoroborate, hexafluoroantimonate,trifluoromethanesulfonate, hexafluoroarsenate, hexafluorophosphate, andarenesulfonate. The onium salts can also be oligomeric or polymericcompounds having multiple onium salt moieties as well as moleculeshaving a single onium salt moiety.

Useful iodonium salts can be simple salts (for example, containing ananion such as chloride, bromide, iodide, or C₄H₅SO₃ ⁻) or a metalcomplex salt (for example, containing SbF₆ ⁻, PF₆ ⁻, BF₄ ⁻,tetrakis(perfluorophenyl)borate, or SbF₅OH₃₁AsF₆ ⁻). Mixtures of any ofthese iodonium salts of the same or different class can be used ifdesired.

The selection of a particular onium salt can be made for optimumproperties with the other essential components and amounts. Particularlyuseful sulfonium salts include but are not limited to,triaryl-substituted salts such as mixed triarylsulfoniumhexafluoroantimonates (for example, commercially available as UVI-6974from Dow Chemical Company), mixed triarylsulfonium hexafluorophosphates(for example, commercially available as UVI-6990 from Dow ChemicalCompany), and arylsulfonium hexafluorophosphates.

One or more onium salts (such as an iodonium salt or a sulfonium salt)are generally present in the non-aqueous metal catalytic composition inan amount of at least 0.05 weight % and up to and including 10 weight %,or typically at least 0.1 weight % and up to and including 10 weight %,or even at least 0.5 weight % and up to and including 5 weight %, allbased on the total amount of components (a) through (c) in thenon-aqueous metal catalytic composition.

Besides onium salts described above, nonionic photoacid generators canbe useful, which compounds include but are not limited to, diazomethanederivatives such as, glyoxime derivatives, bissulfone derivatives,disulfono derivatives, nitrobenzyl sulfonate derivatives, sulfonic acidester derivatives, and sulfonic acid esters of N-hydroxyimides. One ormore nonionic photoacid generators can be present in the non-aqueousmetal catalytic composition in an amount of at least 0.05 weight % andup to and including 10 weight %, or typically at least 0.1 weight % andup to and including 10 weight %, or even at least 0.5 weight % and up toand including 5 weight %, all based on the total amount of components(a) through (c) in the non-aqueous metal catalytic composition.

For free radical photocuring chemistry, the photocurable component canbe one or more free-radically polymerizable compounds to providefree-radically polymerizable functionality, including ethylenicallyunsaturated polymerizable monomers, oligomers, or polymers such asmono-functional or multi-functional acrylates (also includesmethacrylates). Such free-radically polymerizable compounds comprise atleast one ethylenically unsaturated polymerizable bond and they cancomprise two or more of these unsaturated moieties in many embodiments.Suitable materials of this type contain at least one ethylenicallyunsaturated polymerizable bond and are capable of undergoing addition(or free radical) polymerization. Such free radically polymerizablematerials include mono-, di-, or poly-acrylates and methacrylates,co-polymerizable mixtures of acrylate monomers and acrylate oligomers,and vinyl compounds such as styrene and styrene derivatives, diallylphthalate, divinyl succinate, divinyl adipate, and divinyl phthalate.Mixtures of two or more of these free radically polymerizable materialscan be used if desired. Such materials can be purchased from a number ofcommercial sources or prepared using known synthetic methods andstarting materials.

The one or more free radically polymerizable materials can be present inthe non-aqueous metal catalytic compositions in an amount of at least 20weight % and up to and including 60 weight %, based on the total amountof components (a) through (c) in the non-aqueous metal catalyticcomposition.

The photocurable component can also include one or more free radicalphotoinitiators that are also present to generate free radicals in thepresence of the free-radically polymerizable compounds. Such freeradical photoinitiators include any compound that is capable ofgenerating free radicals upon exposure to photocuring radiation used inthe practice of this invention such as ultraviolet or visible radiation.For example, free radical photoinitiators can be selected from triazinecompounds, thioxanthone compounds, benzoin compounds, carbazolecompounds, diketone compounds, sulfonium borate compounds, diazocompounds, and biimidazole compounds, benzophenone compounds,anthraquinone compounds, acetophenone compounds, and others that wouldbe readily apparent to one skilled in the art. Mixtures of suchcompounds can be selected from the same or different classes. Many ofsuch free radical photoinitiators can be obtained from variouscommercial sources.

Such free radical photoinitiators can be present in the non-aqueousmetal catalytic composition in an amount of at least 0.1 weight % and upto and including 10 weight %, or typically at least 1 weight % and up toand including 5 weight %, all based on the total amount of components(a) through (c) in the non-aqueous metal catalytic composition.

In some useful embodiments, the free radical photoinitiators describedabove can also function as a silver ion photoreducing composition in thenon-aqueous metal catalytic composition. In other words, a material usedas part of component (c) can perform as part or all of component (b) inthe non-aqueous metal catalytic composition.

Essential component (c) can be a non-curable polymer that acts as abinder material or if in liquid form, an organic solvent for thenon-aqueous metal catalytic composition. Examples of such polymersinclude but are not limited to polyalkyl methacrylates, poly(vinylacetate), polystyrene, poly(vinyl alcohol), polypropylene, poly(vinylbutyral) (for example, BUTVAR™ resin) and other polyvinyl acetals, andother polymers that would be readily apparent to one skilled in the artfrom this teaching. Useful polymers also include copolymers derived atleast in part from vinyl alcohol or derivatives thereof.

The non-aqueous metal catalytic compositions are generally prepared forcoating, printing, or other means of application by simply admixing,under “safe light” conditions, the essential components (a) through (c)and any optional components described above. Such materials can be mixedand dispersed within suitable inert organic solvents to provide aformulation (or “ink”) in which the inert organic solvents do not reactappreciably with any other components incorporated therein. Examples ofsuitable inert organic solvents include but are not limited to, acetone,dichloromethane, isopropanol, DOWANOL® PM solvent, ethylene glycol, andmixtures thereof. When one or more essential components (a) through (c)or an optional component are in liquid form, such as a component (c),those components can act as the “solvent” for the non-aqueous metalcatalytic composition alone, or used in combination with one or moreinert organic solvents. Inert organic solvent-free metal catalyticcompositions can be prepared by simply dissolving, dispersing, andmixing the essential components (a) through (c) and any optionalcomponents with or without the use of mild heating to facilitatedissolution or dispersion.

When inert organic solvents are used, they can be present in thenon-aqueous metal catalytic composition an amount of at least 1 weight %and up to and including 70 weight % or at least 20 weight % and up toand including 50 weight %, based on the total weight of the non-aqueousmetal catalytic composition. The amount of inert organic solvents can bejudiciously chosen depending upon the particular materials used, themeans for applying the resulting non-aqueous metal catalyticcomposition, and desired properties including composition uniformity.

In some embodiments one or more of the photocurable components ornon-curable polymers acts as an organic solvent medium and no additionalinert organic solvents are purposely added to the non-aqueous metalcatalytic composition.

The non-aqueous metal catalytic composition can further include carbonblack, graphite, graphene, carbon nanotubes, or other sources of carbonif desired in an amount of at least 0.5 weight % based on the totalweight of the essential components (a) through (c) described above.

It is also possible to include carbon-coated metal particles such ascarbon-coated copper particles or carbon-coated silver particles indesirable amounts.

In particularly useful embodiments, the non-aqueous metal catalyticcompositions comprise:

(a) a complex of silver and a hindered aromatic N-heterocycle comprisingreducible silver ions (as described above), in an amount of at least 2weight % and up to and including 90 weight %,

(b) a silver ion photoreducing composition (as described above) in anamount of at least 1 weight % and up to and including 10 weight %, and

(c) a photocurable component, non-curable polymer, or combination of aphotocurable component and a non-curable polymer (all as describedabove) in an amount of at least 10 weight % and up to and including 97weight %,

all amounts based on the total amount of components (a) through (c) inthe non-aqueous metal catalytic composition,

wherein, when component (c) comprises a free radically polymerizablematerial, the non-aqueous metal catalytic composition further comprisesa free radical photoinitiator (as described above).

In some of these embodiments, the non-aqueous metal catalyticcomposition can further comprise one or more inert organic solvents.

Preparing Non-Aqueous Metal Catalytic Compositions

The essential components (a) through (c) described above and anyoptional components, with or without one or more inert organic solventscan be blended to prepare a non-aqueous metal catalytic compositionunder “safe light” conditions if desired. This mixing can occur insuitable inert organic solvents (as described above) if desired. Theresulting non-aqueous metal catalytic composition can be provided inliquid form to have a viscosity of at least 1 centipoise and up to andincluding 100,000 centipoises at 25° C., or it can be provided as a freeflowing powder. The non-aqueous metal catalytic composition can beapplied to a variety of substrates (described above) by conventionalmeans and photocured to the tack-free state within 1 second or up to 10minutes or more.

Examples of suitable inert organic solvents include but are not limitedto, acetone, methanol, ethanol, isopropanol, 1-methoxy-2-propanol,methylene chloride, and any other inert organic solvent that does notreact appreciably with any of the essential components (a) through (c)of the non-aqueous metal catalytic compositions.

Alternatively, a photocurable component can be used as the solvent(s)for mixing of the essential and optional components, or such a liquidmaterial can be used in combination with inert organic solvent(s). Aninert organic solvent can be used also to aid in obtaining a liquidformulation with suitable viscosity for desired methods of applicationto a substrate such as various coating methods, ink jet inks, or othermaterials or operations, such as for printing with relief elements orflexographic printing plates. However, inert organic solvent-free,non-aqueous metal catalytic compositions also can be prepared by simplydissolving or dispersing the essential and any optional components inone of the components that is in liquid form, with or without mildheating.

The amounts of the various components for these formulations aredescribed above for the non-aqueous metal catalytic compositions.

Photoreducing can be achieved by activating (irradiating) thenon-aqueous metal catalytic composition to reduce the reducible silverions and also optionally, to cause polymerization or curing of one ormore photocurable components. This photoreduction can be achieved byexposure to radiant energy such as ultraviolet light as described above.Desirable photoreduction is desirably achieved using UV or visibleirradiation having a wavelength of at least 150 nm to and including 700nm and at intensity of at least 1 mJ/cm² and up to and including 1000mJ/cm² or more typically of at least 1 mJ/cm² and up to and including800 mJ/cm². More details of this process are provided below.

Use of Non-Aqueous Metal Catalytic Compositions

As noted above, the non-aqueous metal catalytic composition can beformed in a suitable manner (uniformly or patternwise) on one or moresupporting sides of a suitable substrate to provide a precursor articlecomprising a metal catalytic layer or a metal catalytic pattern.

The non-aqueous metal catalytic composition can be photocured orphotopolymerized using suitable radiation as described above includingultraviolet light or visible actinic light, or both, to photoreduce thereducible silver ions to silver particles in a fashion corresponding tothe formed metal catalytic layer or metal catalytic pattern. One or moresuitable light sources can be used for the exposure process. Eachprecursor article can be exposed individually as a single element, or inalternative embodiments described below, a web (for example, aroll-to-roll continuous web) of multiple precursor articles in multipleportions of a continuous web of substrate can be exposed as the web ispassed through exposure stations, or the exposure device is passed overthe web. The same or different non-aqueous metal catalytic compositionscan be applied (for example, printed) on both supporting sides of thesubstrate whether it is in the form of a single element or continuousweb. In many embodiments, different conductive metal patterns can beformed on opposing supporting sides of the substrate (or continuousweb).

More specifically, the non-aqueous metal catalytic composition can beapplied in a uniform or pattern-wise manner to any suitable substrateusing any means for application, such as dip coating, roll coating,hopper coating, spray coating, spin coating, ink jetting,photolithographic imprinting, “flexographic” printing using printingelements including flexographic printing members (such as flexographicprinting plates and flexographic printing sleeves), lithographicprinting using lithographic printing plates, and gravure or intaglioprinting using appropriate printing members.

When the non-aqueous metal catalytic composition is uniformly applied toa suitable substrate, it can be “imaged” or selectively exposed (orpatterned) with exposing radiation through a suitable photomask (maskingelement) having the desired pattern, to reduce the silver ions to silverparticles (metal) in a corresponding imagewise fashion. Excessnon-aqueous metal catalytic composition can be then appropriatelyremoved using a suitable “developer” organic solvent medium. Thesefeatures or steps can be carried out on both (opposing) supporting sidesof the substrate.

Suitable substrates (also known as “receiver elements”) can be composedof any suitable material as long as it does not inhibit the purpose ofthe non-aqueous metal catalytic composition. For example, substrates canbe formed from materials including but are not limited to, polymericfilms, metals, glasses (untreated or treated for example withtetrafluorocarbon plasma, hydrophobic fluorine, or a siloxanewater-repellant material), silicon or ceramic wafers, fabrics, papers,and combinations thereof (such as laminates of various films, orlaminates of papers and films) provided that a uniform layer or patternof a non-aqueous metal catalytic composition can be formed thereon in asuitable manner and followed by irradiation on at least one supportivesurface thereof. The substrate can be transparent or opaque, and rigidor flexible. The substrate can include one or more auxiliary polymericor non-polymeric layers or one or more patterns of other materialsbefore the non-aqueous metal catalytic composition is applied accordingto the present invention.

A supportive surface of the substrate can be treated for example with aprimer layer or electrical or mechanical treatments (such as graining)to render that surface “receptive” to improve adhesion of thenon-aqueous metal catalytic composition and resulting photocured metalcatalytic layer or metal catalytic pattern. An adhesive layer can bedisposed on the substrate and this adhesive layer can have variousproperties in response to stimuli (for example, it can be thermallyactivated, solvent activated, or chemically activated) and that servesto provide a receptive layer. Useful adhesive materials of this type aredescribed for example in [0057] of U.S. Patent Application 2008/0233280(Blanchet et al.).

In some embodiments, the substrate comprises a separate receptive layeras a receptive surface disposed on the supportive side of the substrate,which receptive layer and substrate can be composed of a material suchas a suitable polymeric material that is highly receptive of thenon-aqueous metal catalytic composition. Such receptive layer can haveany suitable dry thickness of at least 0.05 μm when measured at 25° C.

The supportive sides of the substrate, especially polymeric substrates,can be treated by exposure to corona discharge, mechanical abrasion,flame treatments, or oxygen plasmas, or by coating with variouspolymeric films, such as poly(vinylidene chloride) or an aromaticpolysiloxane as described for example in U.S. Pat. No. 5,492,730 (Balabaet al.) and U.S. Pat. No. 5,527,562 (Balaba et al.) and U.S. PatentApplication Publication 2009/0076217 (Gommans et al.).

Suitable substrate materials for forming precursor articles according tothe present invention include but are not limited to, metallic films orfoils, metallic films on polymer, glass, or ceramic supports, metallicfilms on electrically conductive film supports, semi-conducting organicor inorganic films, organic or inorganic dielectric films, or laminatesof two or more layers of such materials. For example, useful substratescan include polymeric films such as poly(ethylene terephthalate) films,poly(ethylene naphthalate) films, polyimide films, polycarbonate films,polyacrylate films, polystyrene films, polyolefin films, and polyamidefilms, silicon and other ceramics, metal foils such as aluminum foils,cellulosic papers or resin-coated or glass-coated papers, glass orglass-containing composites, metals such as aluminum, tin, and copper,and metalized films. The substrate can also include one or more chargeinjection layers, charge transporting layers, and semi-conducting layerson which the non-aqueous metal catalytic composition pattern is formed.

Particularly useful substrates are polyesters films such as films ofpoly(ethylene terephthalate), polycarbonate, or poly(vinylidenechloride) films with or without surface-treatments as noted above, orcoatings.

Useful substrates can have a desired dry thickness depending upon theeventual use of the article formed therefrom, for example itsincorporation into various articles or optical or display devices. Forexample, the substrate dry thickness (including all treatments andauxiliary layers) can be at least 0.001 mm and up to and including 10mm, and especially for polymeric films, the substrate dry thickness canbe at least 0.008 mm and up to and including 0.2 mm.

The substrate used to prepare the articles described herein can beprovided in various forms, such as for example, individual sheets in anysize or shape, and continuous webs such as continuous webs oftransparent substrates including transparent polyester substrates thatare suitable for roll-to-roll operations. Such continuous webs can bedivided or formed into individual first, second, and additional portionson one or both supportive sides that can be used to form the same ordifferent photoreduced patterns from the same or different non-aqueousmetal catalytic compositions.

After application of the non-aqueous metal catalytic composition, anyinert organic solvents can be removed by drying or a pre-bakingprocedure that does not adversely affect the remaining components orprematurely cause curing. Useful drying conditions can be as low as roomtemperature for as little as 5 seconds and up to and including severalhours depending upon the manufacturing process. In most processes, suchas roll-to-roll processes described below, the drying conditions can beat high enough temperatures to remove at least 90% of the inert organicsolvent within at least 1 second.

Any formed uniform metal catalytic layer can have a dry thickness of atleast 0.1 μm and up to and including 10 μm, or typically at least 0.2 μmand up to and including 1 μm, and the optimal dry thickness can betailored for the intended use of the resulting uniform photoreducedlayer, which generally has about the same dry thickness as the uniformlayer of the non-photoreduced non-aqueous metal catalytic composition.Such a uniform metal catalytic layer can be applied to both (opposing)supporting sides of the substrate, which uniform layers can have thesame or different metal catalytic compositions or dry thickness.

Any applied pattern of the non-aqueous metal catalytic composition cancomprise a grid of lines (or other shapes including circles or anirregular network) having an average thickness (or width) of at least0.2 μm and up to and including 100 μm, or typically of at least 5 μm andup to and including 10 μm, and the optimal dry thickness (or width) canbe tailored for the intended use of the resulting uniform photoreducedlayer, which generally has about the same dry thickness (or width) asthe grid lines of the non-photoreduced non-aqueous metal catalyticcomposition.

Thus, the present invention provides precursor articles comprising asubstrate and uniform layers or patterns of the non-aqueous metalcatalytic composition, wherein such precursor articles can be thenappropriately exposed (for example as described above at a wavelength ofat least 250 nm and up to and including 700 nm) to photoreduce silverions to silver particles, for example in the presence of oxygen, toprovide intermediate articles with metal catalytic layers or metalcatalytic patterns.

For example, this photoreducing of the reducible silver ions can providesilver particles having an average particle size of at least 10 nm andup to and including 1000 nm (or more likely of least 20 nm and up to andincluding 500 nm), and wherein at least 80% (or even at least 90%) ofthe number of the silver particles have a particle size of at least 10nm and up to and including 100 nm.

During exposure to reduce the silver ions, photocuring can be initiatedwith any photocurable components present in the metal catalytic layer ormetal catalytic pattern, and the resulting silver particles can besurrounded in a photocured matrix derived from the photocurablecomponent and other remaining components.

In some embodiments, the same or different non-aqueous metal catalyticcomposition can be applied in a suitable manner on both supporting sides(main surfaces) of the substrate to form “duplex” or dual-sidedprecursor articles, and each applied non-aqueous metal catalyticcomposition can be in the form of the same or different uniform metalcatalytic layer or metal catalytic pattern.

In many embodiments, a metal catalytic pattern of the metal catalyticcomposition is applied on one or both (opposing) supporting sides of thesubstrate (for example as a roll-to-roll web) using a relief elementsuch as elastomeric relief elements derived from flexographic printingplate precursors, many of which are known in the art and some arecommercially available, for example as the CYREL® FlexographicPhotopolymer Plates from DuPont and the Flexcel SR and NX Flexographicplates from Eastman Kodak Company.

Particularly useful elastomeric relief elements are derived fromflexographic printing plate precursors and flexographic printing sleeveprecursors, each of which can be appropriately imaged (and processed ifneeded) to provide the relief elements for “printing” or applying asuitable metal catalytic pattern.

For example, useful elastomeric relief elements can be comprised of oneor more elastomeric layers, with or without a substrate, in which arelief image can be generated using suitable imaging means.

For example, the elastomeric relief element (for example, flexographicprinting member) having a relief layer comprising an uppermost reliefsurface and an average relief image depth (pattern height) of at least50 μm, or typically having an average relief image depth of at least 100μm relative from the uppermost relief surface, can be prepared fromimagewise exposure of an elastomeric photopolymerizable layer in anelastomeric relief element precursor such as a flexographic printingmember precursor, for example as described in U.S. Pat. No. 7,799,504(Zwadlo et al.) and U.S. Pat. No. 8,142,987 (Ali et al.) and U.S. PatentApplication Publication 2012/0237871 (Zwadlo), the disclosures of all ofwhich are incorporated herein by reference for details of suchflexographic printing member precursors. Such elastomericphotopolymerizable layers can be imaged through a suitable mask image toprovide an elastomeric relief element (for example, flexographicprinting plate or flexographic printing sleeve). In some embodiments,the relief layer comprising the relief pattern can be disposed on asuitable substrate. Other useful materials and image formation methods(including development) for provide elastomeric relief images are alsodescribed in the noted Ali et al. patent. The relief layer can bedifferent if different patterns of non-aqueous metal catalyticcompositions are applied to opposing supporting sides of the substrate.

In other embodiments, the elastomeric relief element is provided from adirect (or ablation) laser-engraveable elastomer relief elementprecursor, with or without integral masks, as described for example inU.S. Pat. No. 5,719,009 (Fan), U.S. Pat. No. 5,798,202 (Cushner et al.),U.S. Pat. No. 5,804,353 (Cushner et al.), U.S. Pat. No. 6,090,529(Gelbart), U.S. Pat. No. 6,159,659 (Gelbart), U.S. Pat. No. 6,511,784(Hiller et al.), U.S. Pat. No. 7,811,744 (Figov), U.S. Pat. No.7,947,426 (Figov et al.), U.S. Pat. No. 8,114,572 (Landry-Coltrain etal.), U.S. Pat. No. 8,153,347 (Veres et al.), U.S. Pat. No. 8,187,793(Regan et al.), and U.S. Patent Application Publications 2002/0136969(Hiller et al.), 2003/0129530 (Leinenback et al.), 2003/0136285 (Telseret al.), 2003/0180636 (Kanga et al.), and 2012/0240802 (Landry-Coltrainet al.), the disclosures of all of which are incorporated herein fordetails of such laser-engraveable precursors.

When the noted elastomeric relief elements are used in the presentinvention, the non-aqueous metal catalytic composition can applied in asuitable manner to the uppermost relief surface (raised surface) in theelastomeric relief element. Application to a substrate can beaccomplished in a suitable procedure and it is desirable that as littleas possible is coated onto the sides (slopes) or recesses of the reliefdepressions. Anilox roller systems or other roller application systems,especially low volume Anilox rollers, below 2.5 billion cubicmicrometers per square inch (6.35 billion cubic micrometers per squarecentimeter) and associated skive knives can be used. Optimum metering ofthe non-aqueous metal catalytic composition onto the uppermost reliefsurface can be achieved by controlling viscosity or thickness, orchoosing an appropriate application means.

For example, the non-aqueous metal catalytic composition can have aviscosity during this application of at least 1 cps (centipoise) and upto and including 5000 cps, or at least 1 cps to and up to and including1500 cps. The thickness of the non-aqueous metal catalytic compositionon the relief image is generally limited to a sufficient amount that canreadily be transferred to a substrate but not too much to flow over theedges of the elastomeric relief element in the recesses duringapplication.

The non-aqueous metal catalytic composition can be fed from an Anilox orother roller inking system in a measured amount for each printedprecursor article. In one embodiment, a first roller can be used totransfer the non-aqueous metal catalytic composition from an “ink” panor a metering system to a meter roller or Anilox roller. The non-aqueousmetal catalytic composition is generally metered to a uniform thicknesswhen it is transferred from the Anilox roller to a printing platecylinder. When the substrate is moved through the roll-to-roll handlingsystem from the printing plate cylinder to an impression cylinder, theimpression cylinder applies pressure to the printing plate cylinder thattransfers an image from an elastomeric relief element to the substrate.

After the non-aqueous metal catalytic composition has been applied tothe uppermost relief surface (or raised surface) of the elastomericrelief element, it can be useful to remove at least 25 weight % of anyinert organic solvents included therein to form a viscous deposit on theuppermost relief surface of the relief image. This removal of inertorganic solvents can be achieved in any manner, for example using jetsof hot air, evaporation at room temperature, or heating in an oven at anelevated temperature, or other means known in the art for removing anorganic solvent.

Once on the substrate, either in a uniform metal catalytic layer orpredetermined metal catalytic pattern of grid lines or other shapes (onone or opposing supporting sides of the substrate), the non-aqueousmetal catalytic composition in the precursor article can be irradiatedwith suitable radiation as described above from a suitable source suchas a fluorescent lamp or LED to provide a silver metal-containing andphotocured metal catalytic layer or a silver metal-containing photocuredmetal catalytic pattern on the substrate. For example, silver ionreduction and any photocuring can be achieved by the use of UV-visibleirradiation having a wavelength (λ_(max)) of at least 150 nm and up toand including 700 nm and at intensity of at least 1,000 microwatts/cm²and up to and including 80,000 microwatts/cm². The irradiation systemused to generate such radiation can consist of one or more ultravioletlamps for example in the form of 1 to 50 discharge lamps, for example,xenon, metallic halide, metallic arc (such as a low, medium or highpressure mercury vapor discharge lamps having the desired operatingpressure from a few millimeters to about 10 atmospheres). The lamps caninclude envelopes capable of transmitting light of a wavelength of atleast 150 tun and up to and including 700 nm or typically at least 240nm and up to and including 450 nm. The lamp envelope can consist ofquartz, such as spectrocil or Pyrex. Typical lamps that can be employedfor providing ultraviolet radiation are, for example, medium pressuremercury arcs, such as the GE H3T7 arc and a Hanovia 450 W arc lamp.Silver ion photoreducing and any photocuring can be carried out using acombination of various lamps, some of or all of which can operate in aninert atmosphere. When using UV lamps, the irradiation flux impingingupon the substrate (or applied layer or pattern) can be at least 0.01watts/inch² (0.0197 watts/cm²) to effect sufficient rapid silver ionphotoreduction and photocuring of the applied non-aqueous metalcatalytic composition within 1 to 20 seconds in a continuous manner, forexample in a roll-to-roll operation.

An LED irradiation device to be used in the photoreduction andphotocuring can have an emission peak wavelength of 350 nm or more. TheLED device can include two or more types of elements having differentemission peak wavelengths greater than or equal to 350 nm. A commercialexample of an LED device that has an emission peak wavelength of 350 nmor more and has an ultraviolet light-emitting diode (UV-LED), isNCCU-033 that is available from Nichia Corporation.

The result of such irradiation of a precursor article is an intermediatearticle comprising the substrate (for example, individual sheets or acontinuous web) and having thereon either a photoreduced and photocuredmetal catalytic layer or a photoreduced or photocured metal catalyticpattern (containing suitable silver particles) on one or both supportingsides of the substrate, each of which is derived from a non-aqueousmetal catalytic composition as described above.

The resulting intermediate articles can be used in this form for someapplications, but in most embodiments, they are further processed toincorporate a conductive metal on the uniform photoreduced andphotocured metal catalytic layer or photoreduced and cured metalcatalytic pattern, each of which includes at least the silver metalparticles as “seed” materials for further application of metals, such asusing electroless metal procedures. For example, photoreduced andphotocured metal catalytic layer or photoreduced and photocured metalcatalytic pattern can include other “seed” metal particles besides the“seed” silver metal particles, including but not limited to, palladium,copper, nickel, and platinum particles, all of which particles can beelectrolessly plated with copper, platinum, palladium, or other metalsdescribed below.

One useful method according to this invention uses multiple flexographicprinting plates (for example, prepared as described above) in a stack ina printing station wherein each stack has its own printing platecylinder so that each flexographic printing plate is used to printindividual substrates, or the stack of printing plates can be used toprint multiple portions in a substrate web (on one or both opposingsupporting sides). The same or different metal catalytic composition canbe “printed” or applied to a substrate (on same or opposing supportingsides) using the multiple flexographic printing plates.

In other embodiments, a central impression cylinder can be used with asingle impression cylinder mounted on a printing press frame. As thesubstrate (or receiver element) enters the printing press frame, it isbrought into contact with the impression cylinder and the appropriatemetal catalytic pattern is printed (formed) using the non-aqueous metalcatalytic composition.

Alternatively, an in-line flexographic printing process can be utilizedin which the printing stations are arranged in a horizontal line and aredriven by a common line shaft. The printing stations can be coupled toexposure stations, cutting stations, folders, and other post-processingequipment. A skilled worker could be readily determined other usefulconfigurations of equipment and stations using information that isavailable in the art. For example, an in-the-round imaging process isdescribed in WO 2013/063084 (Jin et al.).

The intermediate article can be stored with just the metal catalyticlayer or metal catalytic pattern comprising the silver particles for useat a later time.

The intermediate article described herein formed after photoreducing thereducible silver ions to silver particles, can be immediately immersedin an aqueous-based electroless metal plating bath or solution toelectrolessly plate a suitable metal onto the silver particles in themetal catalytic layer or the metal catalytic pattern.

Thus, the intermediate article can be contacted with an electrolessplating metal that is the same as or different from the “seed” silvermetal particles described above. In most embodiments, the electrolessplating metal is a metal different from silver metal particles.

Any metal that will likely electrolessly “plate” on the silver metalparticles can be used at this point, but in most embodiments, theelectroless plating metal can be for example copper(II), silver(I),gold(IV), palladium(II), platinum(II), nickel(II), chromium(II), andcombinations thereof. Copper(II), silver(I), and nickel(II) areparticularly useful electroless plating metals.

The one or more electroless plating metals can be present in anaqueous-based electroless plating bath or solution in an amount of atleast 0.01 weight % and up to and including 20 weight % based on totalsolution weight.

Electroless plating can be carried out using known temperature and timeconditions, as such conditions are well known in various textbooks andscientific literature. It is also known to include various additivessuch as metal complexing agents or stabilizing agents in theaqueous-based electroless plating solutions. Variations in time andtemperature can be used to change the metal electroless platingthickness or the metal electroless plating deposition rate.

A useful aqueous-based electroless plating solution or bath is anelectroless copper(II) plating bath that contains formaldehyde as areducing agent. Ethylenediaminetetraacetic acid (EDTA) or salts thereofcan be present as a copper complexing agent. For example, copperelectroless plating can be carried out at room temperature for severalseconds and up to several hours depending upon the desired depositionrate and plating rate and plating metal thickness.

Other useful aqueous-based electroless plating solutions or bathscomprise silver(I) with EDTA and sodium tartrate, silver(I) with ammoniaand glucose, copper(II) with EDTA and dimethylamineborane, copper(II)with citrate and hypophosphite, nickel(II) with lactic acid, aceticacid, and a hypophosphite, and other industry standard aqueous-basedelectroless baths or solutions such as those described by Mallory et al.in Electroless Plating: Fundamentals and Applications 1990.

After the electroless plating procedure to provide a conductive metallayer or a conductive metal pattern on one or more portions of one oropposing supporting sides of the substrate, the resulting productarticle can be removed from the aqueous-based electroless plating bathor solution and again washed using distilled water or deionized water oranother aqueous-based solution to remove any residual electrolessplating chemistry. At this point, the electrolessly plated metal isgenerally stable and can be used for its intended purpose.

In some embodiments, the resulting product article can be rinsed orcleaned with water at room temperature as described for example in[0048] of WO 2013/063183 (Petcavich), or with deionized water at atemperature of less than 70° C. as described in [0027] of WO 2013/169345(Ramakrishnan et al.).

Thus, a method carried out according to this invention can be used toprovide a product article comprising a substrate and having disposedthereon one or more electrically-conductive patterns (on either or bothsupporting sides) comprising electrically-conductive metals acquired byproviding “seed” silver metal particles by in-situ reduction of silverions followed by electroless plating with more silver or a differentmetal.

To change the surface of the electrolessly plated metal for visual ordurability reasons, it is possible that a variety of post-treatments canbe employed including surface plating of still at least another (thirdor more) metal such as nickel or silver on the first electrolesslyplated metal (this procedure is sometimes known as “capping”), or thecreation of a metal oxide, metal sulfide, or a metal selenide layer thatis adequate to change the surface color and scattering propertieswithout reducing the electrical conductivity of any electrolessly platedmetal. Depending upon the metals used in the various capping procedures,it may be desirable to treat the electrolessly plated metal with a seedmetal catalyst in an aqueous-based seed metal catalyst solution tofacilitate deposition of additional metals.

In addition, multiple treatments with the same or differentaqueous-based electroless metal plating solution can be carried out insequence, using the same or different conditions. Sequential washing orrinsing steps can be also carried out where appropriate at roomtemperature or a temperature less than 70° C.

In some embodiments, a method for providing an electrically-conductiveproduct article comprises:

providing a continuous web of a transparent substrate of any of thosematerials described above, but particularly transparent polymericsubstrates,

providing a metal catalytic pattern on one or more portions of thecontinuous web using a non-aqueous metal catalytic composition asdescribed above, for example applying it using a flexographic printingmember,

exposing the metal catalytic pattern to radiation (as described above)to reduce the silver ions (photoreduction) and optionally photocurephotocurable components in the non-aqueous metal catalytic compositionin the one or more portions of the continuous web, and

electrolessly plating the metal catalytic composition in the one or moreportions of the continuous web with an electrically conductive metal,using electroless plating procedures described above.

Embodiments of this method can be carried out on only one of thesupporting sides of the transparent substrate, or on both supportingsides of the transparent substrate to provide the same or differentelectrically-conductive patterns of electrically conductive metals.

As would be apparent to one skilled in the art, a plurality of portionshaving the same or different electrically-conductive patterns can beprovided on this continuous web (on one or both supporting sides)according to the present invention.

For example, a method for providing a plurality of product articlescomprises:

providing a continuous web of a transparent substrate,

forming a metal catalytic pattern on at least a first portion of thecontinuous web using a non-aqueous metal catalytic composition asdescribed above,

exposing the metal catalytic pattern to photoreducing radiation (asdescribed above) to form silver metal particles in the first portion ofthe continuous web (which first portion can also contain photocuredmaterials),

electrolessly plating the silver metal particles in the first portion ofthe continuous web with an electrically conductive metal (as describedabove), and

repeating these features on one or more additional portions of thecontinuous web that are different from the first portion, using the sameor different non-aqueous metal catalytic composition.

The exposure to photoreducing radiation can be carried out by advancingthe continuous web comprising the first portion comprising the metalcatalytic pattern to be proximate exposing radiation, and therebyphotoreducing the silver ions. Second and additional portions can besimilarly advanced on the continuous web to be proximate exposingradiation to reduce the reducible silver ions in each of the portions.Electroless plating can be carried out immediately, of if desired, theresulting continuous web comprising multiple metal catalytic patternswith silver metal particles can be wound up as a roll for future use.

As would be apparent from other teaching in this disclosure, such methodembodiments can be carried out on opposing supporting sides of thecontinuous web to provide same or different metal catalytic patterns.

The multiple electrically-conductive patterns provided by electrolesslyplating the metal catalytic patterns can be used to form individual ormultiple electrically conductive articles from the continuous web andsuch electrically-conductive articles can be assembled into the same ordifferent individual devices.

Product articles prepared according to the present invention can beformulated into capacitive touch screen sensors that comprise suitableelectrically-conductive grid lines in touch regions, electrodes,electrical leads, and electrically-conductive connectors that provideconnection of electrically-conductive grids with other components of adevice.

Some details of useful methods and apparatus for carrying out thesefeatures are described for example in WO 2013/063183 (Petcavich), WO2013/169345 (Ramakrishnan et al.). Other details of a usefulmanufacturing system for preparing electrically-conductive articlesespecially in a roll-to-roll manner are provided in PCT/US/062366, filedOct. 29, 2012 by Petcavich and Jin, the disclosure of which isincorporated herein by reference.

An additional system of equipment and step features that can be used incarrying out the present invention is described in U.S. Ser. No.14/146,867 filed Jan. 3, 2014 by Shifley, the disclosure of which isincorporated herein by reference for all details that are pertinent tothe present invention.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A method for providing an article, comprising:

providing a metal catalytic layer or a metal catalytic pattern composedof a non-aqueous metal catalytic composition on a substrate, thenon-aqueous metal catalytic composition comprising:

(a) a complex of silver and a hindered aromatic N-heterocycle comprisingreducible silver ions, in an amount of at least 2 weight %,

(b) a silver ion photoreducing composition in an amount of at least 1weight %, and

(c) a photocurable component, a non-curable polymer, or a combination ofa photocurable component and a non-curable polymer,

all amounts being based on the total amounts of components (a) through(c) in the non-aqueous metal catalytic composition,

to provide a precursor article comprising the metal catalytic layer orthe metal catalytic pattern composed of the non-aqueous metal catalyticcomposition.

2. The method of embodiment 1, further comprising:

photoreducing the reducible silver ions to silver particles in the metalcatalytic layer or the metal catalytic pattern.

3. The method of embodiment 2, comprising:

photoreducing the reducible silver ions to silver particles in the metalcatalytic layer or metal catalytic pattern in the presence of oxygen.

4. The method of embodiment 2, comprising:

photoreducing the reducible silver ions to silver particles in the metalcatalytic layer or metal catalytic pattern by imagewise exposure of theprecursor article to radiation having a wavelength of at least 250 nmand up to and including 700 nm.

5. The method of any of embodiments 1 to 4, wherein the silver complexof a hindered aromatic N-heterocycle is represented by the followingstructure:

[Ag_(a)(L)_(b)](X)_(a)

wherein a is 1 or 2; b is 1, 2, or 3; L is a hindered aromaticN-heterocycle, and X is a coordinating or non-coordinating anion.

6. The method of any of embodiments 1 to 5, wherein the complex ofsilver and the hindered aromatic N-heterocycle is one or more of thefollowing AgPy-1 through AgPy-9:

7. The method of any of embodiments 1 to 6, wherein the complex ofsilver and the hindered aromatic N-heterocycle is present in thenon-aqueous metal catalytic composition in an amount of at least 2weight % and up to and including 90 weight %, based on the total amountof components (a) through (c) in the non-aqueous metal catalyticcomposition.

8. The method of any of embodiments 2 to 7, comprising:

photoreducing the reducible silver ions to silver particles having anaverage particle size of at least 10 nm and up to and including 1000 nmand at least 80% of the number of the silver particles have a particlesize of at least 10 nm and up to and including 100 nm.

9. The method of any of embodiments 2 to 8, further comprising, afterphotoreducing the reducible silver ions to silver particles:

electrolessly plating a metal other than silver onto the silverparticles in the metal catalytic layer or metal catalytic pattern.

10. The method of any of embodiments 1 to 9, wherein the non-aqueousmetal catalytic composition further comprises an inert organic solvent.

11. The method of any of embodiments 1 to 10, wherein the photocurablecomponent or non-curable polymer acts as an organic solvent medium andno additional inert organic solvents are purposely added to thenon-aqueous metal catalytic composition.

12. The method of any of embodiments 1 to 11, wherein the non-aqueousmetal catalytic composition comprises:

(a) the complex of silver and the hindered aromatic N-heterocyclecomprising reducible silver ions, in an amount of at least 2 weight %and up to and including 90 weight %,

(b) the silver ion photoreducing composition in an amount of at least 1weight % and up to and including 10 weight %, and

(c) the photocurable component, non-curable polymer, or a combination ofa photocurable component and a non-curable polymer, in an amount of atleast 10 weight % and up to and including 97 weight %,

all amounts based on the total amount of components (a) through (c) inthe non-aqueous metal catalytic composition,

wherein, when component (c) comprises a free radically polymerizablematerial, the non-aqueous metal catalytic composition further comprisesa free radical photoinitiator.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner.

Preparation of a Comparative Photocurable Composition Containing SilverNitrate:

To a mixture of ethoxylated diacrylate (0.5 g, SR259 from Sartomer) andethoxylated pentaerythritol tetraacrylate (0.167 g, SR 494 fromSartomer), photoinitiator and photoreducing agent2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (0.02 g,S9) was added and dissolved at room temperature by sonication in anultrasound bath. To this mixture, a silver nitrate solution (0.4 ml,0.67 g) was added and dissolved by stirring in the dark. In two hours,the viscosity of the formulation significantly increased and in the next2-3 hours, the formulation gelled completely.

Preparation of Silver 2-Phenylpyridine Complex:

To a solution of silver nitrate (1.0 g, 5.9 mmol) dissolved inacetonitrile (10 ml), 2-phenylpyridine (1.83 g, 11.8 mmol) was added andthe reaction mixture was stirred at 70° C. for 30 minutes. The organicsolvent was removed under reduced pressure to obtain a yellow oil ofAg(2-phenylpyridine)₂ ⁺.NO₃ ⁻.

Preparation of Silver 2-(4-methylphenyl)-pyridine Complex:

To a solution of silver nitrate (1.0 g, 5.9 mmol) dissolved inacetonitrile (10 ml), 2-(4-methylphenyl) pyridine (2 g, 11.8 mmol) wasadded and the reaction mixture stirred at 70° C. for 30 minutes. Theorganic solvent was slowly removed at room temperature to obtain a whitecrystalline solid of Ag(2(4-methylphenyl) pyridine)₂ ⁺.NO₃ ⁻. Thecrystal structure of the desired silver complex is shown in FIG. 1.

Preparation of Silver 2-(4-methylphenyl)-benzoxazoline Complex:

To a solution of silver nitrate (1.0 g, 5.9 mmol) dissolved inacetonitrile (10 ml), 2-(4-methylphenyl) benzoxazoline (2.46 g, 11.8mmol) was added and the reaction mixture was stirred at 70° C. for 30minutes. The organic solvent was removed slowly at room temperature toobtain a reddish crystalline solid of Ag(2(4-methylphenyl)benzoxazoline)₂ ⁺.NO₃″. The crystal structure of the desired silvercomplex is shown in FIG. 2.

Preparation of Silver 2,6-Dimethyl Pyridine Complex:

To a solution of silver nitrate (1.0 g, 5.9 mmol) dissolved inacetonitrile (10 ml), 2,6-dimethylpyridine (1.3 g, 12 mmol) was addedand the reaction mixture stirred at 70° C. for 30 minutes. The organicsolvent was slowly removed at room temperature to obtain a reddishcrystalline solid of Ag(2,6-dimethyl pyridine)₂ ⁺.NO₃ ⁻. The crystalstructure of the desired silver complex is shown in FIG. 3.

Inventive Example 1

This example demonstrates that complexes of silver and hindered aromaticN-heterocycles containing reducible silver ions as described above areuseful in non-aqueous metal catalytic composition for in situphotogeneration of “seed” silver particles. The generated silverparticles are very effective catalysts for electroless plating ofcopper.

Preparation of Non-aqueous Metal Catalytic Composition ContainingAg(2-Phenylpyridine)₂ ⁺.NO₃ ⁻ Complex:

To a mixture of 1,1,1-trimethylolpropane triacrylate (1.66 g, SR351,Sartomer) and ethoxylated (30) bisphenol A dimethacrylate (3.33 g, SR9036A, Sartomer), photoinitiator and photoreducing composition2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (0.3 g, ˜5weight %) was added and dissolved at room temperature in chloroform (0.5ml) in an ultrasound bath. To this mixture, the Ag(2-phenylpyridine)₂⁺.NO₃ ⁻ complex described above (0.75 g, ˜12 weight %) was added anddissolved by stirring in the dark to form a non-aqueous metal catalyticcomposition according to the present invention.

Photogeneration of Silver Particles in Thin Film According to thePresent Invention:

The non-aqueous metal catalytic composition described above was spincoated onto a poly(ethylene terephthalate) film substrate at 1500 rpmfor 30 seconds to provide a precursor article that was then exposed tolight from a medium pressure Hg/Xe lamp for 2 seconds. The coating colorchanged from colorless to dark yellow in the resulting intermediatearticle. An absorption spectrum of the coating was recorded showing aclear plasmonic band at 420 nm due to the formation of silvernanoparticles.

Electroless Copper Plating:

The exposed intermediate article described above was immersed in anelectroless copper plating bath solution from obtained from ENTHONE®(Enplate LDS CU-406 SC) at 45° C. for 2 minutes using conditionsrecommended by the commercial supplier. The resulting product articlewas taken out of the bath, rinsed with water, and dried. A clear coatingof metallic copper was observed on the surface of the product articleand its surface resistivity was measured.

Inventive Example 2

This example demonstrates that a very low level of silver complex isneeded to provide sufficient silver particles for efficient electrolessplating of copper.

Preparation of Non-aqueous Metal Catalytic Composition ContainingAg(2-Phenylpyridine)₂ ⁺.NO₃ ⁻ Complex:

To a mixture of 1,1,1-trimethylolpropane triacrylate (1.66 g, SR351,Sartomer) and ethoxylated (30) bisphenol A dimethacrylate (3.33 g, SR9036A, Sartomer), photoinitiator and photoreducing composition2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (0.3 g, ˜5weight %) was added and dissolved at room temperature in chloroform (0.5ml) in an ultrasound bath. To this mixture, the Ag(2-phenylpyridine)₂⁺.NO₃ ⁻ complex described above (0.1 g, ˜2 weight %) was added anddissolved by stirring in the dark.

Photogeneration of Silver Particles in Thin Film:

The non-aqueous metal catalytic composition described above was spincoated onto a poly(ethylene terephthalate) film substrate at 1500 rpmfor 30 seconds to provide a precursor article that was then exposed tolight from a medium pressure Hg/Xe lamp for 2 seconds to provide anintermediate article. The coating color changed from colorless to darkyellow during exposure and an absorption spectrum of the coating wasrecorded (FIG. 4) showing a clear plasmonic band at 420 nm due to theformation of silver nanoparticles.

Electroless Copper Plating:

The intermediate article described above was immersed in an electrolesscopper plating bath solution from ENTHONE® (Enplate LDS CU-406 SC) at45° C. for 5 minutes using conditions recommended by the commercialsupplier. The resulting product article was taken out of the bath,rinsed with water, and dried. A clear coating of metallic copper wasseen on the surface of the product article and its surface resistivitywas measured.

Inventive Example 3

Fine lines of nominal width 7-10 μm of the non-aqueous metal catalyticcomposition described above in Invention Example 2 were printed on apoly(ethylene terephthalate) film substrate using a flexographic testprinter IGT F1 and flexographic printing members obtained fromcommercially available

Kodak Flexcel NX photopolymer plates, and imaged using a mask that waswritten using the Kodak Square Spot laser technology at a resolution of12,800 dpi.

The printed precursor article was exposed to UV light using Fusionbenchtop conveyor unit equipped with H-bulb as a nominal UV dose ofbetween 50-100 mJ/cm² to provide an intermediate article.

This intermediate article was immersed in an electroless copper platingbath, ENTHONE® Enplate LDS CU-406 SC, at 45° C. and 5 minutes usingconditions by the commercial supplier. The resulting product article wastaken out of the bath, rinsed with water, and dried. Micrographs of theprinted and electrolessly plated product article showed clear printedmetallic copper lines as seen in FIG. 5.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. A method for providing an article, comprising: providing a metalcatalytic layer or a metal catalytic pattern composed of a non-aqueousmetal catalytic composition on a substrate, the non-aqueous metalcatalytic composition comprising: (a) a complex of silver and a hinderedaromatic N-heterocycle comprising reducible silver ions, in an amount ofat least 2 weight %, (b) a silver ion photoreducing composition in anamount of at least 1 weight %, and (c) a photocurable component, anon-curable polymer, or a combination of a photocurable component and anon-curable polymer, all amounts being based on the total amounts ofcomponents (a) through (c) in the non-aqueous metal catalyticcomposition, to provide a precursor article comprising the metalcatalytic layer or the metal catalytic pattern composed of thenon-aqueous metal catalytic composition.
 2. The method of claim 1,further comprising: photoreducing the reducible silver ions to silverparticles in the metal catalytic layer or the metal catalytic pattern.3. The method of claim 2, comprising: photoreducing the reducible silverions to silver particles in the metal catalytic layer or metal catalyticpattern in the presence of oxygen.
 4. The method of claim 2, comprising:photoreducing the reducible silver ions to silver particles in the metalcatalytic layer or metal catalytic pattern by imagewise exposure of theprecursor article to radiation having a wavelength of at least 250 nmand up to and including 700 nm.
 5. The method of claim 1, wherein thesilver complex of a hindered aromatic N-heterocycle is represented bythe following structure:[Ag_(a)(L)_(b)](X)_(a) wherein a is 1 or 2; b is 1, 2, or 3; L is ahindered aromatic N-heterocycle, and X is a coordinating ornon-coordinating anion.
 6. The method of claim 1, wherein the complex ofsilver and the hindered aromatic N-heterocycle is one or more of thefollowing AgPy-1 through AgPy-9:


7. The method of claim 1, wherein the complex of silver and the hinderedaromatic N-heterocycle is present in the non-aqueous metal catalyticcomposition in an amount of at least 2 weight % and up to and including90 weight %, based on the total amount of components (a) through (c) inthe non-aqueous metal catalytic composition.
 8. The method of claim 2,comprising: photoreducing the reducible silver ions to silver particleshaving an average particle size of at least 10 nm and up to andincluding 1000 nm and at least 80% of the number of the silver particleshave a particle size of at least 10 nm and up to and including 100 nm.9. The method of claim 2, further comprising, after photoreducing thereducible silver ions to silver particles: electrolessly plating a metalother than silver onto the silver particles in the metal catalytic layeror metal catalytic pattern.
 10. The method of claim 1, wherein thenon-aqueous metal catalytic composition further comprises an inertorganic solvent.
 11. The method of claim 1, wherein the photocurablecomponent or non-curable polymer acts as an organic solvent medium andno additional inert organic solvents are purposely added to thenon-aqueous metal catalytic composition.
 12. The method of claim 1,wherein the non-aqueous metal catalytic composition comprises: (a) thecomplex of silver and the hindered aromatic N-heterocycle comprisingreducible silver ions, in an amount of at least 2 weight % and up to andincluding 90 weight %, (b) the silver ion photoreducing composition inan amount of at least 1 weight % and up to and including 10 weight %,and (c) the photocurable component, non-curable polymer, or acombination of a photocurable component and a non-curable polymer, in anamount of at least 10 weight % and up to and including 97 weight %, allamounts based on the total amount of components (a) through (c) in thenon-aqueous metal catalytic composition, wherein, when component (c)comprises a free radically polymerizable material, the non-aqueous metalcatalytic composition further comprises a free radical photoinitiator.13. The method of claim 12, wherein the non-aqueous metal catalyticcomposition further comprises an inert organic solvent.
 14. The methodof claim 12, wherein the complex of silver and a hindered aromaticN-heterocycle is a silver-benzthiazole complex, silver-pyrimidinecomplex, silver-pyrazine complex, silver benzoxazole complex, or acombination thereof.